Method of making light-blocking high opacity articles

ABSTRACT

A method for providing a foamed, opacifying element includes providing a foamable aqueous compositions, aerating it to a foam density of 0.1-0.5 g/cm 3 , applying the foamed aqueous composition to a porous substrate, drying, and densifying the dried layer Such foamable aqueous compositions have 0.05-15 weight % of porous particles; at least 20 weight % of a binder; at least 0.0001 weight % of additives (including a surfactant); water; and at least 0.001 weight % of an opacifying colorant. Each porous particle includes a continuous polymeric phase and discrete pores; a mode particle size of 2-50 μm; and a porosity of 20-70 volume %. The continuous polymeric phase T g  is&gt;80° C. and has a polymer viscosity of 80-500 centipoises at an ethyl acetate shear rate of 100 sec −1  at a concentration of 20 weight % at 25° C.

RELATED APPLICATIONS

Reference is made to the following copending and commonly assignedpatent applications:

U.S. Ser. No. 15/144,893 (filed May 3, 2016 by Brick, Nair, and McHugh)that is a continuation-in-part of commonly assigned U.S. Ser. No.14/730,280, filed Jun. 4, 2015 by Brick, Nair, Lindner, and Pyszczek,now abandoned.

U.S. Ser. No. 15/144,875 (filed May 3, 2016 by Nair, Brick, andPyszczek), recently allowed, that is a continuation-in-part of commonlyassigned U.S. Ser. No. 14/730,269, filed Jun. 4, 2015 by Brick, Nair,Lindner, and Pyszczek, now abandoned;

U.S. Ser. No. 15/144,911 (filed May 3, 2016 by Brick, Nair, Lindner, andBessey) that is also a continuation-in-part of commonly assigned U.S.Ser. No. 14/730,280, filed Jun. 4, 2015 by Brick, Nair, Lindner, andPyszczek, now abandoned;

U.S. Ser. No. 15/______ (filed on even date herewith by Nair, Brick, andPyszczek) and entitled “Foamable and Foamed Aqueous Compositions”(Attorney Docket K002082/JLT); and

U.S. Ser. No. 15/______ (filed on even date herewith by Nair, Brick, andSedita) and entitled “Light-blocking Articles with High OpacifyingLayer” (Attorney Docket K002105/JLT);

the disclosures of all of which applications are incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates to methods of making foamed, opacifying elementsusing a foamable aqueous composition that is suitably foamed and appliedto a porous substrate. Such foamed, opacifying elements havelight-blocking properties as well as light coloration.

BACKGROUND OF THE INVENTION

In general, when light strikes a surface, some of it may be reflected,some absorbed, some scattered, and the rest transmitted. Reflection canbe diffuse, such as light reflecting off a rough surface such as a whitewall, in all directions, or specular, as in light reflecting off amirror at a definite angle. An opaque substance transmits almost nolight, and therefore reflects, scatters, or absorbs all of it. Bothmirrors and carbon black are opaque. Opacity depends on the frequency ofthe light being considered. “Blackout” or light blocking materialstypically refer to coated layers in articles that are substantiallyimpermeable to light such as visible or UV radiation. Thus, when ablackout material such as a blackout curtain is hung over a window, itgenerally blocks substantially all external light from entering the roomthrough that window. Blackout materials are suitable as curtains andshades for domestic use, for institutional use in hospitals and nursinghomes, as well as for use in commercial establishments such as hotels,movie theaters, and aircraft windows where the option of excluding lightcan be desirable.

Light blocking articles such as the blackout curtains can be comprisedof a fabric (porous) substrate coated with more than one layer of afoamed latex composition. There is a desire for these curtains, inaddition to blocking transmitted light, to have a light color (hue)facing the environment when an activity needs illumination so as tominimize the amount of artificial lighting needed to perform theactivity. An example is when the function of the blackout material is toseparate two areas of activity where one or both areas can beartificially lit at the same time. However, more often than not, thefunction of a blackout curtain is to prevent sunlight from entering aroom through a building window. It can also be desirable for the color(hue) of the back side to match the external decor of the building.

Light colored blackout curtains can be made by coating a fabric withlight colored foams containing light scattering pigments such astitanium dioxide or clays. However, very thick foam coatings will beneeded to create blackout curtains through which the sun is not visiblein a darkened room using only these pigments. One method that is used toreduce the weight of such blackout materials is to sandwich alight-absorbing, foamed black or grey pigment, such as carbon blacklayer between two light scattering, white pigment-containing layers.

When an electromagnetic radiation blocking coating has, as it oftendoes, a strongly light absorbing material containing black pigments suchas carbon black, between two reflective layers, it has at least twodistinct problems. First, such materials require three separate coatingoperations that reduce manufacturing productivity and increase unitcosts. Secondly, carbon black in the light absorbing middle layer canbecome “fugitive” (or non-enclosed) from some puncture or tear occurringduring sewing or laundering, and soil other layers such as thereflective layers, which is highly objectionable. Additionally, thestitches generated in the materials during sewing can cause the fugitivecarbon from the light absorbing layer to spread over a larger areathereby increasing the area of objectionable shading of the lightcolored surface.

U.S. Pat. No. 7,754,409 (Nair et al.), U.S. Pat. No. 7,887,984 (Nair etal.), U.S. Pat. No. 8,252,414 (Putnam et al.), and U.S. Pat. No.8,329,783 (Nair et al.) describe porous polymer particles that are madeby a multiple emulsion process, wherein the multiple emulsion processprovides formation of individual porous particles comprising acontinuous polymer phase and multiple discrete internal pores, and suchindividual porous particles are dispersed in an external aqueous phase.The described Evaporative Limited Coalescence (ELC) process is used tocontrol the particle size and distribution while a hydrocolloid isincorporated to stabilize the inner emulsion of the multiple emulsionthat provides the template for generating the pores in the porousparticles.

U.S. Patent Application Publication 2015/0234098 (Lofftus et al.)describes improved articles that are designed with an opacifying layerthat is capable of blocking predetermined electromagnetic radiation. Theopacifying layer is disposed on a substrate that can be composed of anysuitable material and a porous or non-porous underlying layer can beincorporated between the substrate and the opacifying layer. While thesearticles have numerous advantages and represent an important advance inthe art, there is a need for further improvement in providing opacifyingarticles that are lighter in weight; and that have improved flexibility,good “hand,” while maintaining light coloration of the surfaces facingan observer without losing reflectivity, and light-absorptiveproperties; launderability; and minimizing dark opacifying agentsgetting out into the environment upon stitching and handling.

An improvement in this art is provided by the foamed aqueouscompositions described and claimed in recently allowed U.S. Ser. No.15/144,875 (noted above) in which very small amounts of opacifyingcolorants can be incorporated into porous particles, and the resultingcomposition has a foam density of at least 0.1 g/cm³.

While the noted foamed compositions and foamed, opacifying elementsdescribed in the previous commonly assigned patent applications providean advance in the art, there is continued need for improvements. Thereis a need for a way to provide superior opacifying compositions andarticles containing porous particles that provide improved lightscattering and opacity to a dry opacifying layer by maintaining theporosity and pores in the porous particles during high temperaturedrying and long residence times in the dryers, after applying the foamedaqueous composition on porous substrates. There is also a need toprovide higher porosity derived from a large number of smaller poresthat can result in better light scattering to provide greaterluminosity.

SUMMARY OF THE INVENTION

The present invention provides a method for providing a foamed,opacifying element, the method comprising:

providing a foamable aqueous composition that has at least 35% solidsand up to and including 70% solids, and comprises:

(a) at least 0.05 weight % and up to and including 15 weight % of porousparticles, each porous particle comprising a continuous polymeric phaseand a first set of discrete pores dispersed within the continuouspolymeric phase, the porous particles having a mode particle size of atleast 2 μm and up to and including 50 μm and a porosity of at least 20volume % and up to and including 70 volume %, and the continuouspolymeric phase having a glass transition temperature greater than 80°C. and comprising a polymer having a viscosity of at least 80centipoises and up to and including 500 centipoises at a shear rate of100 sec⁻¹ in ethyl acetate at a concentration of 20 weight % at 25° C.,

(b) at least 20 weight % of a binder material;

(c) at least 0.0001 weight % of one or more additives comprising asurfactant;

(d) water;

(e) at least 0.001 weight % of an opacifying colorant different from allof the (c) additives, which opacifying colorant absorbs predeterminedelectromagnetic radiation,

all amounts based on the total weight of the foamable aqueouscomposition;

aerating the foamable aqueous composition to provide a foamed aqueouscomposition having a foam density of at least 0.1 g/cm⁻¹ and up to andincluding 0.5 g/cm³;

disposing the foamed aqueous composition onto a surface of at least onesupporting side of a porous substrate;

drying and at least partially curing, simultaneously or in any order,the foamed aqueous composition to provide a dry foamed composition; and

densifying the dry foamed composition to provide a dry opacifying layerin a foamed, opacifying element.

In some embodiments of the inventive method, the foamable aqueouscomposition has at least 40% solids and up to and including 60% solids,and wherein:

the continuous polymeric phase comprises at least 70 weight % and up toand including 100 weight %, based on the total polymer weight in thecontinuous polymeric phase, of one or more polymers derived from one ormore of cellulose acetate, cellulose butyrate, cellulose acetatebutyrate, and cellulose acetate propionate;

the porous particles are present in an amount of at least 0.5 weight %and up to and including 10 weight %; the binder material is present inan amount of at least 30 weight % and up to and including 50 weight %and has a glass transition temperature of less than 25° C.;

the one or more (c) additives further comprise an optical brightener inan amount of at least 0.01 weight % and up to and including 2 weight %;and

carbon black is present as at least one opacifying colorant in an amountof at least 0.003 weight % and up to and including 0.2 weight %,

all amounts being based on the total weight of the foamable aqueouscomposition.

The present invention provides a number of advantages. In addition tothe advantages described in U.S. Ser. No. 15/144,875 (noted above), thepresent invention utilizes foamable and foamed aqueous compositions toprovide foamed, opacifying elements (light-blocking articles) containinglow amounts of opacifying colorants, which compositions and elements arenot damaged by temperatures greater than 100° C. that may occur duringthe drying operations consistent with manufacture thereof. Moreover, thefoamed, opacifying elements (such as light-blocking curtains and shades)according to the present invention exhibit desired opacity, bright andlight coloration, and improved flexibility, “hand”, and drapeability.Manufacturing operations can be readily carried out in a continuousmanner for example, in a roll-to-roll operation using a web of poroussubstrate.

It highly important also to consider that the foamed, opacifyingelements prepared according to this invention can have simplerconstruction than light-blocking articles described in the prior art.For example, such elements can comprise a single dry opacifying layerthat is both opacifying and light in color at the same time, disposed ona porous substrate compared to prior art articles that comprise two ormore dry layers including a dry opacifying layer and a light-coloredlayer in a sandwich construction. Such multiple pass prior artconstructions are designed necessarily to hide the black color of theopacifying colorant in the dry opacifying layer.

The present invention avoids such thick and expensive constructionswhile providing the noted advantages with very little opacifyingcolorant (for example, less than 1 weight % of total solids). Becausethe opacifying colorant can be contained within the porous particles andthere is so little of the opacifying colorant used, the foamed,opacifying element remains light-colored and when it is damaged orpunctured, the escape of opacifying colorant and its effect on othermaterials are minimized. Moreover, with very little opacifying colorantused according to the present invention, its impact to absorb infraredradiation (heat) and radiate that heat into the environment is minimizedalong with the pores that can scatter or reflect heat back towards itssource. Thus, the elements according to the present invention assist theuser to manage heat in environments where this is a major concern suchas hospital rooms and in extreme climates.

In some embodiments, the foamed, opacifying elements prepared accordingto the present invention can comprise a single dry opacifying layer thathas all of the antimicrobial, opacifying, and flame retardantproperties.

DETAILED DESCRIPTION OF THE INVENTION

The following discussion is directed to various embodiments of thepresent invention and while some embodiments can be desirable forspecific uses, the disclosed embodiments should not be interpreted orotherwise considered be limit the scope of the present invention, asclaimed below. In addition, one skilled in the art will understand thatthe following disclosure has broader application than is explicitlydescribed for any specific embodiment.

Definitions

As used herein to define various components of the foamed aqueouscomposition and foamable aqueous composition, or materials used toprepare the porous particles, unless otherwise indicated, the singularforms “a,” “an,” and “the” are intended to include one or more of thecomponents (that is, including plurality referents).

Each term that is not explicitly defined in the present application isto be understood to have a meaning that is commonly accepted by thoseskilled in the art. If the construction of a term would render itmeaningless or essentially meaningless in its context, the termdefinition should be taken from a standard dictionary.

The use of numerical values in the various ranges specified herein,unless otherwise expressly indicated otherwise, are considered to beapproximations as though the minimum and maximum values within thestated ranges were both preceded by the word “about.” In this manner,slight variations above and below the stated ranges can be used toachieve substantially the same results as the values within the ranges.In addition, the disclosure of these ranges is intended as a continuousrange including every value between the minimum and maximum values.

Unless otherwise indicated, the terms “foamed, opacifying element,”“element,” and “article” are intended to refer to the same material.

Unless otherwise indicated, the terms “foamed aqueous composition” and“composition” are intended to refer to the same material.

The terms “porous particle” and “porous particles” are used herein,unless otherwise indicated, to refer to porous organic polymericmaterials useful in the foamable aqueous compositions, foamed aqueouscompositions, and foamed opacifying elements according to the presentinvention. The porous particles generally comprise a solid continuouspolymeric phase having an external particle surface and discrete poresdispersed within the continuous polymeric phase. The continuouspolymeric phase also can be chemically crosslinked or elastomeric innature, or both chemically crosslinked and elastomeric in nature.

The continuous polymeric phase of the porous particles generally has thesame composition throughout that solid phase. That is, the continuouspolymeric phase is generally uniform in composition including anyadditives (for example, colorants) that can be incorporated therein. Inaddition, if mixtures of polymers are used in the continuous polymericphase, generally those mixtures also are dispersed uniformly throughout.

The term “porogen” refers to a pore forming agent used to make porousparticles for use in the present invention. For example, in the practiceof the present invention, a porogen can be the aqueous phase ofwater-in-oil emulsions (that is in the first emulsion), along with apore stabilizing hydrocolloid, or any other additive in the aqueousphase that can act as the template for creation of pores and modulatethe porosity of the porous particles.

As used in this disclosure, the term “isolated from each other” refersto the different (distinct) pores of same or different sizes that areseparated from each other by some of the continuous polymeric phase, andsuch pores are not generally interconnected.

The terms “first discrete pore” and “second discrete pore” refer todistinct sets of isolated pores in the porous particles. These first andsecond discrete pores can refer to distinct individual pores, or in mostembodiments, they refer to distinct sets of pores. Each distinct set ofpores includes a plurality of pores, each of which pores is isolatedfrom others pores in the set of pores, and the pores of each set ofpores are isolated from all other pores of the other sets of pores inthe porous particle. Each set of pores can have the same mode averagesize or both sets can have the same mode average size. The word“discrete” is also used to define different droplets of the first andsecond aqueous phases when they are suspended in the oil (solvent) phase(described below).

The porous particles can include “micro,” “mesa,” and “macro” discretepores, which according to the International Union of Pure and AppliedChemistry, are the classifications recommended for discrete pore sizesof less than 2 nm, from 2 nm to 50 nm, and greater than 50 nm,respectively. Thus, while the porous particles can include closeddiscrete pores of all sizes and shapes (that is, closed discrete poresentirely within the continuous polymeric phase) providing a suitablevolume in each discrete pore, macro discrete pores are particularlyuseful. While there can be open macro pores on the surface of the porousparticle, such open pores are not desirable and can be present only byaccident. The size of the porous particle, the formulation, andmanufacturing conditions are the primary controlling factors fordiscrete pore size. However, typically the discrete pores independentlyhave an average size of at least 100 nm and up to and including 7,000nm, or more likely at least 200 nm and up to and including 2,000 nm.Whatever the size of the discrete pores, they are generally distributedrandomly throughout the continuous polymeric phase. If desired, thediscrete pores can be grouped predominantly in one part (for example,“core” or “shell”) of the porous particles.

In some embodiments, where there are different sets of discrete pores,the discrete pores of a first set are predominantly nearer then externalparticle surface compared to the discrete pores of a second set. Forexample, a set of smaller discrete pores can be predominantly close tothe external particle surface compared to a set of larger discretepores. As used herein, the term “predominant” means that a larger numberfraction of pores of one size is found in a “shell” area nearer thesurface of the porous particle than one would expect based on the totalnumber fraction of the two or more types (sizes) of pores present in theporous particle.

The porous particles used in this invention generally have a porosity ofat least 20 volume % and up to and including 70 volume %, or likely atleast 40 volume % and up to and including 65 volume %, or more typicallyat least 45 volume % and up to an including 60 volume %, all based onthe total porous particle volume. Porosity can be measured by the knownmercury intrusion technique.

“Opacity” is a measured parameter of a foamed, opacifying elementaccording to the present invention that characterizes the extent oftransmission of electromagnetic radiation such as visible light. Agreater opacity indicates a more efficient blocking (hiding) ofpredetermined radiation (as described below). In the present invention,the “opacity” of a foamed, opacifying element is quantitated bymeasuring the light blocking value (LBV), described below with theExamples, which determines the extent to which the impinging radiationor light is blocked by the foamed, opacifying element. The higher theLBV, the greater the light blocking ability exhibited by the foamed,opacifying element.

Glass transition temperatures of the organic polymers used to preparethe continuous polymeric phase can be measured using DifferentialScanning Calorimetry (DSC) using known procedures. For many commerciallyavailable organic polymers, the glass transition temperatures are knownfrom the suppliers.

Polymer viscosity (in centipoises) comprising the continuous polymericphase can be measured in ethyl acetate at concentration of 20 weight %of the polymer at 25° C. in an Anton Parr MCR 301 stress rheometer in acoquette using steady shear sweeps. Shear rate at 100 sec⁻¹ wascalculated from the resulting graphical plot of viscosity vs. shearrate.

CIELAB L*, a*, and b* values described herein have the known definitionsaccording to CIE 1976 color space or later known versions of color spaceand were calculated assuming a standard D65 illuminant. The Ytristimulus value of the X, Y, and Z tristimulus values was used as ameasure of the luminous reflectance or “brightness” of a dry opacifyinglayer.

Uses

The foamable aqueous compositions and foamed aqueous compositions can beused to prepare foamed, opacifying elements that in turn can be usefulas radiation blocking materials to provide blackout curtains, carpets,banners, and window shades for airplanes, labels, projection screens,textile fabrics, and packaging materials. The foamed, opacifyingelements can also exhibit improved sound and heat blocking properties.The term “blackout curtain” is intended to include but not limited to,window curtains, shades for all purposes, draperies, room dividers,privacy curtains, and cubicle curtains suitable for various environmentsand structures. The foamed, opacifying elements exhibit blackoutproperties and can optionally have an opaque printable surface able toaccept ink using in screen printing, inkjet printing, or other printingprocesses. Thus, one can provide opposing printable surfaces in suchmaterials (elements) with the same opacity as if only one side wasprinted, with no printed image on one side showing through the otherside.

Foamable Aqueous Compositions

The foamable aqueous compositions can be suitably aerated to providefoamed aqueous compositions, for example to prepare a foamed, opacifyingelement as described below. In many embodiments, the foamable aqueouscompositions used in the present invention have five essentialcomponents, that is, the only components needed to obtain the propertiesof the foamed, opacifying element described herein: (a) porous particlesas described below; (b) a binder material, also described below; (c) oneor more additives as described below, comprising at least onesurfactant; (d) water; and (e) an opacifying colorant different from allof the compounds of component (c), which opacifying colorant absorbs“predetermined electromagnetic radiation” (generally UV to near-IR, forexample, absorbing the radiation of all wavelengths of from 350 nm to800 nm or from 350 nm to and including 700 nm). Optional (non-essential)components that can be included are also described below.

The foamable aqueous composition according to this invention generallyhas at least 35% and up to and including 70% solids, or moreparticularly at least 40% and up to and including 60% solids.

Porous Particles:

Porous particles used in the present invention containing discrete pores(or compartments) are used in the opacifying layers and they aregenerally prepared, as described below, using one or more water-in-oilemulsions in combination with an aqueous suspension process, such as inthe Evaporative Limited Coalescence (ELC) process. The details for thepreparation of the porous particles are provided, for example, in U.S.Pat. No. 8,110,628 (Nair et al.), U.S. Pat. No. 8,703,834 (Nair), U.S.Pat. No. 7,754,409 (Nair et al.), U.S. Pat. No. 7,887,984 (Nair et al.),U.S. Pat. No. 8,329,783 (Nair et al.), and U.S. Pat. No. 8,252,414(Putnam et al.), the disclosures of all of which are incorporated hereinby reference. Thus, the porous particles are generally polymeric andorganic in nature (that is, the continuous polymeric phase is polymericand organic in nature) and non-porous particles (having less than 5%porosity) are excluded. Inorganic particles can be present on the outersurface as noted below.

The porous particles are composed of a continuous polymeric phasederived from one or more organic polymers that are chosen so that thecontinuous polymeric phase has a glass transition temperature (T_(g)) ofgreater than 80° C., or more typically of at least 100° C. and up to andincluding 180° C., or more likely at least 110° C. and up to andincluding 170° C. as determined using Differential Scanning Calorimetry.Polymers having a T_(g) that is greater than 200° C. are typically lessuseful in the continuous polymeric phase.

In addition, the continuous polymeric phase comprises one or morepolymers each of which has a viscosity of at least 80 centipoises and upto and including 500 centipoises at a shear rate of 100 sec⁻¹ asmeasured in ethyl acetate at a concentration of 20 weight % at 25° C.This feature is important to optimize the preparation of porousparticles used in the practice of this invention so that the preparedporous particles have a narrow particle size distributions and highporosity.

For example, the continuous polymeric phase can comprise one or morepolymers having the properties noted above, wherein generally at least70 weight % and up to and including 100 weight % based on the totalpolymer weight in the continuous polymeric phase, is composed of one ormore cellulose polymers (or cellulosic polymers) including but notlimited to, those cellulosic polymers derived from one or more ofcellulose acetate, cellulose butyrate, cellulose acetate butyrate, andcellulose acetate propionate. A polymer derived solely from celluloseacetate butyrate is particularly useful. Mixtures of these cellulosepolymers can also be used if desired, and mixtures comprising a polymerderived from cellulose acetate butyrate as at least 80 weight % of thetotal of cellulose polymers (or of all polymers in the continuouspolymeric phase) are particularly useful mixtures.

In general, the porous particles used in the present invention have amode particle size equal to or less than 50 μm, or of at least 2 μm andup to and including 50 μm, or typically of at least 3 μm and up to andincluding 30 μm or even up to and including 40 μm. Most useful porousparticles have a mode particle size of at least 3 μm and up to andincluding 20 μm. Mode particle size represents the most frequentlyoccurring diameter for spherical particles and the most frequentlyoccurring largest diameter for the non-spherical particles in a particlesize distribution histogram.

Pore stabilizing materials such as hydrocolloids can be present withinat least part of the volume of the discrete pores distributed throughoutthe continuous polymeric phase, which pore stabilizing materials aredescribed in patents cited above. In some embodiments, the same porestabilizing material is incorporated in essentially all of the discretepores throughout the entire porous particles. In many embodiments, thepore stabilizing hydrocolloids are selected from the group consisting ofcarboxymethyl cellulose (CMC), a gelatin, a protein or proteinderivative, polyvinyl alcohol and its derivatives, a hydrophilicsynthetic polymer, and a water-soluble microgel.

It can be desired in some embodiments to provide additional stability ofone or more discrete pores in the porous particles during theirformation, by having one or more amphiphilic block copolymers disposedat the interface of the one or more discrete pores and the continuouspolymeric phase. Such materials are “low HLB”, meaning that they have anHLB (hydrophilic-lipophilic balance) value as it is calculated usingknown science, of 6 or less, or even 5 or less. The details of theseamphiphilic polymers and their use in the preparation of the porousparticles are provided in U.S. Pat. No. 9,029,431 (Nair et al.), thedisclosure of which is incorporated herein by reference.

A particularly useful amphiphilic block copolymer useful in suchembodiments comprises poly(ethyleneoxide) and poly(caprolactone) thatcan be represented as PEO-b-PCL. Amphiphilic block copolymers, graftcopolymers and random graft copolymers containing similar components arealso useful.

Such an amphiphilic block copolymer can be generally present in theporous particles in an amount of at least 1 weight % and up to andincluding 99.5 weight %, or at least 2 weight % and up to and including50 weight %, based on total porous particle dry weight.

The porous particles used in this invention can be spherical ornon-spherical depending upon the desired use. In a method used toprepare the porous particles, additives (shape control agents) can beincorporated into the first or second aqueous phases, or in the oil(organic) phase to modify the shape, aspect ratio, or morphology of theporous particles. The shape control agents can be added prior to orafter forming the water-in-oil-in-water emulsion. In either case, theinterface at the oil and second water phase is modified before organicsolvent is removed, resulting in a reduction in sphericity of the porousparticles. The porous particles used in the present invention can alsocomprise surface stabilizing agents, such as colloidal silica, on theouter surface of each porous particle, in an amount of at least 0.1weight %, based on the total dry weight of the porous particle.

The average size of the discrete pores (or individually isolated andclosed voids or compartments) is described above.

The porous particles can be provided as powders, or as aqueoussuspensions (including water or water with water-miscible organicsolvents such as alcohols). Such powders and aqueous suspensions canalso include surfactants or suspending agents to keep the porousparticles suspended or when rewetting them in an aqueous medium. Auseful surfactant for this purpose, for example is a C₁₂-C₁₄ secondaryalcohol derivative of poly(ethylene oxide) that can be commerciallyavailable as TERGITOL® 15-S-7 (Dow Chemical Corporation). The othercompositional features are described in the incorporated description ofmethods for preparing the porous particles.

The porous particles are generally present in the foamable aqueouscomposition in an amount of at least 0.05 weight % and up to andincluding 15 weight %, or typically at least 0.5 weight % and up to andincluding 10 weight %, based on the total weight of the foamable aqueouscomposition (including water that is present), particularly when theporous particles have a mode size of at least 3 μm and up to andincluding 30 μm.

It is known in the art, that typical white inorganic pigments such astitanium dioxide block electromagnetic radiation by light scattering asa result of refractive index differences between the inorganic pigmentparticles and the surroundings influenced by the pigment particle size.Additionally, there is only so much volume that can be filled (0.635 ofrandom close packing of monodispersed spheres) before interstitialcavities form between packed pigment particles.

The opacity of an opacifying layer is enhanced by interstitial voidsthat are formed when the particle volume concentration (PVC), typicallypigment particles such as titanium dioxide, is above a critical level.The sizes of the interstitial voids for example between the pigmentparticles are smaller than the pigment particles themselves and decreasewith increasing polydispersity of such pigment particles. Since thepigment particle sizes are optimized for maximum light scattering whendispersed in a polymeric matrix above the critical PVC, the interstitialvoids created by the pigment particles will be too small to alsooptimally scatter light. Crowding occurs when the spacing betweenpigment S particles decreases to the point where the light scatteringbecomes dependent on the concentration of the pigment particles and theeffectiveness of scattering by the pigment particles is reduced as thepigment loading is increased. This is known as “dependent scattering,” aphenomenon whereby the effective scattering diameter, or scatteringzones, of pigment particles become effectively greater than their actualdiameter. These scattering zones overlap as the concentration ofscattering pigment particles increases, reducing scattering efficiency,and resulting in the crowding effect. Small and large pigment particlesize extenders have been used in an attempt to create greater separationbetween the scattering pigment particles and to reduce the overlap ofthe scattering zones to result in greater scattering efficiency andopacity.

Advantageously, for the porous particles used in the present invention,the spacing between the light scattering discrete pores within theporous particles is controlled during the process of forming them and isnot subject to subsequent formulation effects such as dependentscattering effects.

Optimal dry opacifying layers designed according to the presentinvention comprise: porous particles containing a small amount of anopacifying colorant as described below to enhance the light blockingcapacity of the porous particles (particularly transmitted lightblocking capacity); a binder material to hold the porous particles inplace; and surfactants and other additives including optionally one ormore tinting colorants that can be in other porous particles ordispersed within the layer. The foamed aqueous composition used toprepare the dry opacifying layer comprises foam cells that surround theporous particles.

Upon drying the foamed aqueous composition, the large mismatch inrefractive index between the discrete pores of the porous particles inthe dry opacifying layer and the polymer walls (continuous polymericphase), and the dried foam cells, causes incident electromagneticradiation passing through the dry opacifying layer to be scattered bythe multiplicity of interfaces and discrete pores. The back scatteredelectromagnetic radiation can again be scattered and returned in thedirection of the incident electromagnetic radiation thus reducing theattenuation and contributing to the opacifying power and brightness orluminous reflectance of the dry opacifying layer. If a small amount ofelectromagnetic radiation absorbing opacifying colorant is present inthe porous particles of the dry opacifying layer, for example either inthe discrete pores or in the continuous polymer phase of the porousparticles, the opacifying power of the dry opacifying layer isincreased. This is because the multiple scattering of electromagneticradiation in the dry opacifying layer increases the path length of theelectromagnetic radiation through the dry opacifying layer, therebyincreasing the chance that the electromagnetic radiation will encounterthe opacifying colorant in the dry opacifying layer and be blocked orabsorbed by it.

A single dry opacifying layer present in embodiments according to thepresent invention comprises porous particles and a relatively low amountof a predetermined electromagnetic radiation absorbing opacifyingcolorant such as carbon black for creating electromagnetic radiationblocking coatings and the dry foam cells surrounded by the bindermaterial. Multiple light scattering effects by and among the porousparticles and the surrounding dry foam cells, increase the path of theradiation through the dry opacifying layer. The likelihood of radiationencountering an opacifying colorant is increased by this greater pathlength.

Some particularly useful porous particles comprise a continuouspolymeric phase and a first set of discrete pores dispersed within thecontinuous polymeric phase, wherein:

each porous particle has a mode particle size of at least 3 μm and up toand including 30 μm,

each porous particle has a porosity of at least 40 volume % and up toand including 65 volume %,

the continuous polymeric phase comprises one or more polymers, at least70 weight % of which are derived from one or more of cellulose acetate,cellulose butyrate, cellulose acetate butyrate, and cellulose acetatepropionate such that the continuous polymeric phase has a glasstransition temperature (T_(g)) of at least 110° C. and up to andincluding 170° C. as determined using Differential Scanning Calorimetry,

the average size of the discrete pores is at least 50 nm and up to andincluding 1000 nm,

the porous particles further comprise a pore stabilizing hydrocolloidwithin at least part of the volume of the discrete pores, which porestabilizing hydrocolloid is selected from the group consisting ofcarboxymethyl cellulose, a gelatin, a protein or protein derivative,polyvinyl alcohol or a derivative thereof, a hydrophilic syntheticpolymer, and a water-soluble microgel, and

the porous particles comprise one or more amphiphilic low HLB blockcopolymers disposed at the interface of one or more of the discretepores and the continuous polymeric phase.

Binder Materials:

The foamable and foamed aqueous compositions used in the present alsocomprises one or more binder materials (that can behave as a “matrix”for all of the materials in the compositions and resulting dryopacifying layer) to hold the essential porous particles, additives,opacifying colorants, and any optional materials together uponapplication to the porous substrate and drying to form a dry opacifyinglayer.

It is particularly useful that the binder material have the followingproperties: (a) it is water-soluble or water-dispersible; (b) it iscapable of forming a stable foamed aqueous composition with theessential and optional components described herein; (c) it is capable ofbeing disposed onto a suitable substrate as described below; (d) it doesnot inhibit the aeration (foaming) process (described below); (e) it iscapable of being dried and where desired also crosslinked (or cured);(f) it has good light and heat stability; (g) it is film-forming butcontributes to the flexibility of the foamed, opacifying element and isthus not too brittle, for example having a T_(g) of less than 25° C.

The choice of binder material can also be used to increase thelaundering properties of the resulting foamed opacifying compositions inthe foamed, opacifying elements. In addition, the binder material can beused to provide a supple feel to touch and flexibility especially whendisposed on a porous substrate (for example, a fabric) that is meant forwindow coverings such as draperies. The binder material is useful in thefoamed, opacifying element for binding together and adhering the porousparticles and other materials in the dry foamed composition onto theporous substrate.

The binder material can include one or more organic polymers that arefilm forming and that can be provided as an emulsion, dispersion, or anaqueous solution, and that cumulatively provide the properties notedabove. It can also include polymers that are self-crosslinking orself-curable, or it can include one or more polymers to whichcrosslinking agents are added and are thus curable or capable of beingcrosslinked (or cured) under appropriate conditions.

Thus, if the binder material is crosslinkable (or curable) in thepresence of a suitable crosslinking agent, such crosslinking (or curing)can be activated chemically with heat, radiation, or other known means.A curing or crosslinking agent serves to provide improved insolubilityof the resulting dry foamed composition, cohesive strength, and adhesionto the porous substrate. The curing or crosslinking agent is generally achemical having functional groups capable of reacting with reactivesites in a binder material (such as a functionalized latex polymer)under curing conditions to thereby produce a crosslinked structure.Representative crosslinking agents include but are not limited to,multi-functional aziridines, aldehydes, methylol derivatives, andepoxides.

Useful binder materials include but are not limited, to poly(vinylalcohol), poly(vinyl pyrrolidone), ethylene oxide polymers,polyurethanes, urethane-acrylic copolymers, other acrylic polymers,styrene-acrylic copolymers, vinyl polymers, styrene-butadienecopolymers, acrylonitrile copolymers, polyesters, silicone polymers, ora combination of two or more of these organic polymers. Such bindermaterials are readily available from various commercial sources or canbe prepared using known starting materials and synthetic conditions. Thebinder material can be anionic, cationic or nonionic in net charge. Auseful class of film-forming binder materials includes aqueous latexpolymer dispersions such as acrylic latexes that can be ionic ornonionic colloidal dispersions of acrylate polymers and copolymers. Forexample, useful film-forming aqueous latexes include but are not limitedto, styrene-butadiene latexes, poly(vinyl chloride) and poly(vinylidenechloride) latexes, poly(vinyl pyridine) latexes, poly(acrylonitrile)latexes, and latexes formed from N-methylol acrylamide, butyl acrylate,and ethyl acrylate. Examples of suitable commercially available bindermaterials include those sold by DSM under the trade names NEOREZ®A-1150, NEOCRYL® A-6093, by Dow under the trade name RHOPLEX® NW-1845Kand by BASF under the tradenames BUTOFAN® N S144, and BUTOFAN® NS 222,by Lubrizol under the tradenames HYSTRETCH® and HYCAR®, and resins soldby Royal Adhesives such as PARANOL® AC-2032.

The binder material generally has a glass transition temperature that isless than 25° C., and more likely equal to or less than 0° C. Glasstransition temperature can be determined using known procedures and suchvalues are already known for many polymers useful as binder materials inthis invention. The binder material desirably has adequate flexibilityand tensile strength in order to maintain integrity upon handling,especially for use with porous textile substrates.

The one or more binder materials can be present in the foamable aqueouscomposition in an amount of at least 20 weight %, or at least 20 weight% and up to and including 60 weight %, or typically at least 30 weight %and up to and including 50 weight %, based on the total foamable aqueouscomposition (that is, the total weight of all components includingwater).

Additives:

The foamable aqueous compositions can include at least 0.0001, or atleast 0.001 weight %, or even at least 0.01 weight %, and up to andincluding 2 weight %, or up to and including 5 weight %, or even up toand including 20 weight %, or even at least and including 30 weight % ofone or more additives comprising at least one surfactant as definedbelow. Other useful additives include but are not limited toplasticizers, inorganic or organic pigments and dyes (for example,pigment or dye colorants different from the opacifying colorantsdescribed below), flame retardants, biocides, fungicides, antimicrobialagents, preservatives, pH buffers, optical brighteners, tintingcolorants, metal particles such as metal platelets or metal flakes,thickeners, and inorganic fillers (such as clays) that are not any ofthe other additive materials or opacifying colorants described below.These amounts refer to the total of all of the one or more additives ina given foamable aqueous composition and are based on the total weightof those compositions (including water). There can be mixtures of eachtype of additive, or mixtures of two or more types of additives in eachof these compositions.

Any of these additives or mixtures thereof, can be present within anylocation of the foamed aqueous composition, including but not limitedto: the continuous polymeric phase; a volume of the first set (or otherset) of discrete pores; or both the first set (or other set) of discretepores and the continuous polymeric phase of the porous particles.Alternatively, the one or more additives can be present within thebinder material alone, or both within the binder material and within theporous particles.

In all embodiments, the (c) additives useful in the present inventionare not the same compounds as the (a) porous particles, (b) bindermaterials, and (d) opacifying colorants as described herein.

As noted above, at least one additive is a surfactant that is defined asa compound that reduces surface tension in a composition. In mostembodiments of this invention, this essential surfactant is a foamingagent that functions to create and enhance foam formation. In many suchembodiments, the one or more (c) additives comprise one or more foamingagents (surfactants) as well as one or more foam stabilizing agents thatare also surface active agents that function to structure and stabilizethe foam. Examples of useful foaming agents (surfactants) and foamstabilizing dispersing agents include but are not limited to, ammoniumstearate, sodium lauryl sulfate, ammonium lauryl sulfate, ammoniumsulfosuccinate, disodium stearyl sulfosuccinate, ethoxylated alcohols,ionic, nonionic or anionic agents such as fatty acid soaps or a fattyacid condensation product with an alkylene oxide, for example, thecondensation product of ethylene oxide with lauryl or oleic acid or anester of fatty alcohols and similar materials, many of which can beobtained from various commercial sources. Mixtures of foaming agents canbe used if desired.

The relative amounts of each of these two types of (c) additives is notcritical as long as the desired function is evident, that is suitablefoaming properties as required to prepare the foamed aqueous compositionof the present invention, and stability of that foamed aqueouscomposition during storage and manufacture of the foamed, opacifyingelements. The optimal amounts of each of these additives can bedetermined by using routine experimentation and the teaching in theworking Examples below.

Other useful (c) additives include metal particles that can be obtainedfrom any available commercial source as metal flakes or metal plateletsand in dry form or as a suspension. Such metal flakes or metal plateletsare substantially 2-dimensional particles, having opposing main surfacesor faces separated by a relatively minor thickness dimension. The metalflakes can have a size range of at least 2 μm and up to and including 50μm in main surface equivalent circular diameter (ECD) wherein the ECD isthe diameter of a circle having the same area as the main face. Examplesof useable metal flakes include those available from Ciba SpecialtyChemicals (BASF) such as aluminum flakes that are available as METASHEEN91-0410 in ethyl acetate, and copper flakes that can be obtained fromvarious commercial sources. Further details of useful metal flakes areprovided in Cols. 11-12 of U.S. Pat. No. 8,614,039 (Nair et al.), thedisclosure of which is incorporated herein by reference. The metalparticles described above, and particularly the metal flakes can be inthe foamable aqueous composition in any suitable location but they areparticularly useful when incorporated within the porous particles suchas within the volume of the discrete pores of the porous particles.

Useful biocides (that is, antimicrobial agents or antifungal agents)that can be present as (c) additives include but are not limited to,silver metal (for example, silver particles, platelets, or fibrousstrands) and silver-containing compounds such as silver chelates andsilver salts such as silver sulfate, silver nitrate, silver chloride,silver bromide, silver iodide, silver iodate, silver bromate, silvertungstate, silver phosphate, and silver carboxylates. In addition,copper metal (for example, copper particles, platelets, or fibrousstrands) and copper-containing compounds such as copper chelates andcopper salts can be present as (c) additives for biocidal purposes.Mixtures of any of silver metal, silver-containing compounds, coppermetal, and copper-containing compounds, can also be present and used inthis manner.

It can also be useful to include thickeners as (c) additives in order tomodify the viscosity of the foamable aqueous composition and tostabilize it as long as aeration is not inhibited. A skilled worker canoptimize the viscosity so as to obtain optimal aeration conditions anddesired foam density as described below. Useful thickeners can beutilized to control the rheology of the foamable aqueous compositiondepending upon the method used to form the dry opacifying layer on aporous substrate as described below. Particularly useful rheologymodifiers are RHEOVIS® PU 1214 (BASF) and ACRYSOL® G111 (Dow ChemicalCompany).

Particularly useful (c) additives comprise one or more tinting colorantsthat can be used to provide a specific observable color, coloration, orhue in the resulting foamed, opacifying elements. These materials arenot chosen to provide the opacifying property described below for theopacifying colorants and thus, tinting colorants are intended to bedifferent materials than the opacifying colorants.

Mixtures of tinting colorants can be present in the foamable aqueouscompositions and they can be different in composition and amount fromeach other. The desired coloration or hue can be obtained using specifictinting colorants can be used in combination with opacifying colorant(s)described below to offset or modify the original color of a foamed,opacifying element (without such materials) to provide more whiteness(or brightness) in the final “color” (or coloration). The one or moretinting colorants can be incorporated within the porous particles(either within the volume of discrete pores, within the continuouspolymeric phase, or in both places) or they can be uniformly dispersedwithin the binder material. In some embodiments, a tinting colorant canbe incorporated within the same porous particles that also include anopacifying colorant (as described below). Alternatively, one or moretinting colorants can be present within both the porous particles (in asuitable location) and within the binder material.

In some embodiments, a first population of porous particles describedherein comprising opacifying colorants as described below, and anotherpopulation of porous particles described herein comprising tintingcolorants can be mixed with the first population of porous particles.The two sets of porous particles can comprise the same or differentpolymers in the continuous polymeric phase.

The one or more tinting colorants can be present in the foamable aqueouscomposition in an amount of at least 0.0001 weight %, or more typicallyat least 0.001 weight %, and up to and including 3 weight %, based onthe total weight of the foamable aqueous composition (including water).Tinting colorants can be dyes or organic pigments that are soluble ordispersible in organic solvents and polymers that are used for makingthe porous particles and thus can be included within the oil phase usedto prepare such porous particles. Alternatively, the tinting colorantscan be primarily water-soluble or water-dispersible materials andincluded into an aqueous phase used to prepare the porous particles.

It can also be useful to include one or more optical brighteners as (c)additives to increase the whiteness (brightness or “fluorescent” effect)of the final coloration in the foamed, opacifying element. Opticalbrighteners are sometimes known in the art as “fluorescent whiteners” or“fluorescent brighteners.” In general, such materials are organiccompounds selected from classes of known compounds such as derivativesof stilbene and 4,4′-diaminostilbene (such as bistriazinyl derivative);derivatives of benzene and biphenyl (such as styril derivatives);pyrazolines; derivatives of bis(benzoxazole-2-yl); coumarins;carbostyrils; naphthalimides; s-triazines; and pyridotriazoles. Specificexamples of optical brighteners can be found in various publicationsincluding “Fluorescent Whitening Agents,” Kirk-Othmer Encyclopedia ofChemical Technology, Fourth Edition, volume 11, Wiley & Sons, 1994. Oneof more of such compounds can be present in an amount of at least 0.01weight % and up to and including 2 weight %, all based on the totalweight of the foamable aqueous composition.

When present, one or more optical brighteners can be in one or morelocations in the foamed aqueous composition. For example, an opticalbrightener can be present in the binder material. Alternatively, anoptical brightener can be present within: the continuous polymeric phaseof the porous particles; a volume of the first set (or any other set) ofdiscrete pores in the porous particles; or both in a volume of the firstset (or any other set) of discrete pores and the continuous polymericphase, of the porous particles.

In many useful embodiments, the (c) additives comprise two or morematerials selected from surfactant that is a foaming agent, a foamstabilizing agent, a tinting agent, an optical brightener, flameretardants, an antimicrobial agent, and an inorganic filler (such as aclay).

Water:

Water is the primary solvent used in the foamable aqueous compositionsused in the present invention. By “primary” is meant that of the totalweight of solvents, water comprises at least 75 weight %, and morelikely at least 80 weight % and up to and including 100 weight % of thetotal solvent weight. Auxiliary solvents that can be present must notadversely affect or harm the other components in the composition, namelythe porous particles, binder materials, one or more additives, andopacifying agents. Nor must such auxiliary solvents adversely affectformation of the foamable aqueous composition or its use to prepare afoamed, opacifying element. Such auxiliary solvents can bewater-miscible organic solvents such as alcohols and ketones.

The solvents then, primarily water, comprise at least 30 weight % and upto and including 65 weight %, or typically at least 40 weight % and upto and including 60 weight %, of the total weight of the foamableaqueous composition.

Opacifying Colorants:

The opacifying colorants used in the present invention can be a singlecolorant or chosen from any suitable combination of colorants such thatthe single or multiple colorants form the “opacifying colorant” thatabsorbs predetermined electromagnetic radiation (defined above) toprovide blackout properties (or suitable opacity). Opacifying colorantscan be soluble dyes or pigments or combinations of each or both types ofmaterials. The opacifying colorants are different from all of thecompounds defined above as the (c) additives.

In most embodiments, the one or more opacifying colorants are presentwithin a volume of the first set (or another set) of discrete poreswithin the porous particles, within the continuous polymeric binder ofthe porous particles, or within both the volume of the first set (oranother set) of discrete pores and the continuous polymeric binder ofthe porous particles. This is highly advantageous as the porousparticles can be used to “encapsulate” various opacifying colorants aswell as tinting colorants and other (c) additives so they are keptisolated from the other components of the foamable aqueous compositionand are additionally not exposed to the environment during sewing orupon surface damage of the foamed, opacifying element. However, in someembodiments, it can be useful to incorporate opacifying agents solely oradditionally within the binder material in which the porous particlesare dispersed.

As used herein, an “opacifying colorant” includes one or more colorantmaterials that are chosen, individually or in combination, to providethe blocking of predetermined electromagnetic radiation (as describedabove). While the opacifying colorants can provide some coloration ordesired hue, they are not purposely chosen for the purpose and are thusmaterials that are chosen to be different from the tinting colorantsdescribed above.

Examples of opacifying colorants that can be used individually or incombination include but are not limited to, neutral or black pigments ordyes, a carbon black, black iron oxide, graphite, aniline black,anthraquinone black, and combinations of colored pigments or dyes suchas combinations of two or more cyan, magenta, green, orange, blue, red,and violet dyes. The present invention is not limited to only thespecific opacifying colorants described herein but these are consideredas representative and as suitable guidance for a skilled worker todevise other combinations of opacifying colorants for the desiredabsorption in the predetermined electromagnetic radiation. A carbonblack or a neutral or black pigment or dye (or combination thereof) isparticularly useful as an opacifying colorant, of which there are manytypes available from commercial sources. Combinations of dyes orpigments such as a combination of the subtractive primary coloredpigments (cyan, magenta, and yellow colored pigments) can also be usedto provide a “black” or visually neutral opacifying colorant.

The opacifying colorant can be generally present in the foamable aqueouscomposition in an amount of at least 0.001 weight % and up to andincluding 0.5 weight %, or even at least 0.003 weight % and up to andincluding 0.2 weight %, all based on the total weight of the foamableaqueous composition (including the weight of solvent). These amountsrefer to the total amount of one or a mixture of opacifying colorants.For example, as noted above, an opacifying colorant can comprise acombination of two or more component colorants (such as a combination ofdyes or a combination of pigments) designed in hues and amounts so thatthe combination meets the desired properties described herein.

In particular embodiments, the opacifying colorant is a carbon blackthat is present in an amount of at least 0.003 weight % and up to andincluding 0.2 weight %, based on the total weight of the foamableaqueous composition.

In some embodiments, the opacifying colorants, if in pigment form, aregenerally milled to a fine particle size and then encapsulated withinthe volume of the discrete pores of the porous particles byincorporating the milled pigment within an aqueous phase used in makingthe porous particles. Alternatively, the opacifying colorant can beincorporated within the continuous polymeric phase of the porousparticles by incorporating the opacifying colorant in the oil phase usedin making the porous particles. Such arrangements can be achieved duringthe manufacture of the porous particles using the teaching providedherein and teaching provided in references cited herein.

In some embodiments, it can be useful to incorporate or dispose at least95% (by weight) of the total opacifying colorant (or combination ofcomponent colorants) within the porous particles (either in the volumeof the discrete pores, continuous polymeric phase, or both), and toincorporate the remainder, if any, within the binder material. However,in many embodiments, 100 weight % of the opacifying colorant isincorporated within the porous particles. For example, more than 50weight % of the total opacifying colorant can be disposed orincorporated within the continuous polymeric phase of the porousparticles, and the remainder can be incorporated within the volume ofthe discrete pores.

The opacifying colorants useful in the practice of this invention can beincorporated into the volume of the discrete pores of individual porousparticles for example, by incorporating them in a first water phase toform a water-in-oil emulsion or in the continuous polymeric phase of theindividual porous particles by incorporating them in the oil phase. In aparticular embodiment, an opacifying colorant can be incorporated intothe first aqueous phase in the form of a milled solid particledispersions of the opacifying colorant. Preparation of milled solidparticle dispersions can include combining the opacifying colorantparticles to be reduced in size with a dispersant and a liquid mediumsuch as water or ethyl acetate (when the opacifying colorant isincorporated in the continuous polymeric phase of the particle) in whichthe porous particles are to be dispersed, in a suitable grinding mill inwhich the porous particles are reduced in size and dispersed. Thedispersant, an important ingredient in the milling, can be chosen toallow the opacifying colorant particles to be milled in the liquidmedium down to a size small enough for incorporation into the discretepores of the porous particles. The dispersants can be selected to obtainefficient opacifying colorant particle size reduction during milling,provide good colloidal stability of the opacifying colorant particles toprevent agglomeration after milling and impart the desired properties ofthe final foamed aqueous composition containing the opacifying colorantsand the porous particles containing them. Alternatively, the opacifyingcolorant also can be incorporated in the continuous polymeric phase as amaster batch of the opacifying colorant and an appropriate resin.

Foamed Aqueous Compositions

Foamed aqueous compositions can be prepared using the proceduresdescribed below wherein an inert gas (such as air) is mechanicallyincorporated into the foamable aqueous composition as described above,which procedures are designed to provide a foam density of at least 0.1g/cm² and up to and including 0.5 g/cm³, or more likely of at least 0.15g/cm³ and up to and including 0.4 g/cm³. Foam density can be determinedgravimetrically by weighing a known volume of the foamed aqueouscomposition.

The foamed aqueous composition according to this invention generally hasat least 35% solids and up to and including 70% solids, or moreparticularly at least 40% solids and up to and including 60% solids.

The essential components (a) through (f) of the foamed aqueouscomposition are generally present in the same amounts as in the foamableaqueous composition (described above) as the foaming process does notappreciably add to or diminish the amounts of such components.

For example, the (a) porous particles (as described above) can bepresent in the foamed aqueous composition in an amount of at least 0.05weight % and up to and including 15 weight %, or typically of at least0.5 weight % and up to and including 10 weight %, based on the totalweight of the foamed aqueous composition.

One or more (b) binder materials (as described above) can be present inan amount of at least 20 weight %, or at least 25 weight % and up to andincluding 70 weight % or typically of at least 30 weight % and up to andincluding 50 weight %, based on the total weight of the foamed aqueouscomposition. In addition, one or more of the binder materials in thefoamed aqueous composition can be curable.

One or more (c) additives (as described above) can be present in anamount of at least 0.0001 weight % and up to and including 30 weight %or typically of at least 0.001 weight %, or even at least 0.01 weight %,and up to and including 20 weight %, based on the total weight of thefoamed aqueous composition. At least one of the (c) additives is asurfactant as described above, and in particularly useful embodiments,the (c) additives comprise a foaming agent and a foam stabilizing agent.Other useful (c) additives can be present as noted above for thefoamable aqueous compositions, also in the amounts noted above. Forexample, some particularly useful embodiments of the foamed aqueouscomposition, the (c) additives comprise two or more materials selectedfrom surfactant that is a foaming agent, a surfactant that is a foamdispersing agent, a tinting agent, an optical brightener, a flameretardant, an antimicrobial agent, and an inorganic filler (such as aclay).

Water is also present as the predominant solvent (at least 75 weight %of total solvent weight), and all of the solvents that are present in anamount of at least 30 weight % and up to and including 70 weight %, ortypically at least 40 weight % and up to and including 60 weight %,based on the total weight of the foamed aqueous composition.

The (e) opacifying colorants (as described above) are generally presentin any suitable amount to provide the desired appearance, coloration,and opacity in the resulting foamed (and dried) opacifying element. Inmany embodiments, the one or more opacifying colorants can be present inan amount of at least 0.001 weight % or at least 0.001 weight % and upto and including 0.5 weight %, or even in an amount of least 0.003weight % and up to and including 0.2 weight %, especially when theopacifying colorant is a carbon black, all weights based on the totalweight of the foamed aqueous composition.

In some embodiments, the foamed aqueous composition comprises at least0.5 weight % and up to and including 10 weight % of the porous particles(as described above) that have a mode particle size of at least 3 μm andup to and including 30 μm, the amount based on the total weight of thefoamed aqueous composition. In addition, discrete pores in such porousparticles can have an average pore size of at least 100 nm and up to andincluding 7000 nm.

Moreover, the foamed aqueous composition can further comprise at least0.001 weight % of the opacifying colorant (described above) within theporous particles. For example, some opacifying colorant can be a carbonblack and present in an amount of at least 0.003 weight % and up to andincluding 0.2 weight % based on the total weight of the foamed aqueouscomposition.

Such opacifying colorant can be within: (i) the continuous polymericphase of the porous particles; (ii) a volume of the first set (oradditional set) of discrete pores; or (iii) both the volume of the firstset (or additional set) of discrete pores and the continuous polymericphase of the porous particles.

In some embodiments of the foamed aqueous composition, porous particlescan be used that further comprise at least a second set of discretepores (different from a “first” set of discrete pores) and an opacifyingcolorant or a tinting colorant can be present within: the continuouspolymeric phase, the volume of the second set of discrete pores, or inboth the continuous polymeric phase and the volume of the second set ofdiscrete pores. First and second sets (or additional sets) of discretepores can be incorporated into the porous particles using manufacturingtechnology described in several references cited above, including U.S.Pat. No. 8,110,628 (Nair et al.).

Foamed, Opacifying Elements

Foamed, opacifying elements can be prepared using methods describedbelow according to the present invention. Such articles comprise aporous substrate and at least one dry foamed composition disposed on atleast one supporting side of the porous substrate to form a dryopacifying layer. As described in more detail, each porous substrate hastwo supporting (planar) sides, that is, a first supporting side and asecond opposing supporting side.

Each of the dry foamed compositions is derived from a foamed aqueouscomposition described above according to the present invention. In allembodiments, each dry foamed composition comprises at least thefollowing essential components (a) through (e) and amounts, all of whichare described in more detail above. In some embodiments, the dry foamedcomposition also comprises the (f) component describe herein.

Component (a) porous particles are present in an amount of at least 0.1weight % and up to and including 40 weight % or at least 0.5 weight %and up to and including 10 weight % of porous particles that aredescribed in detail above, the amounts based on the total weight of thedry foamed composition, particularly when the porous particles have amode particle size of at least 2 μm and up to and including 50 μm (or atleast 3 μm and up to and including 30 μm) and the first set of discretepores of the porous particles have an average pore size of at least 100nm and up to and including 7,000 nm.

In addition, the dry foamed composition includes component (b) bindermaterial in an at least partially cured or crosslinkable form, which isat least 10 weight % and up to and including 70 weight %, or at least 20weight % and up to and including 60 weight % of one or more at leastpartially cured binder materials. Such at least partially cured bindermaterials are derived by at least partial curing or crosslinking(described below) of the binder materials described above. The notedamounts are based on the total weight of the dry foamed composition.Each of the one or more binder materials has a T_(g) of 25° C. or less,or 0° C. or less.

One or more (c) additives, at least one is a surfactant, are present inan amount of at least 0.2 weight % and up to and including 50 weight %,or at least 1 weight % and up to and including 45 weight %, suchadditives being selected from the group consisting of foaming agents,foam stabilizing agents, plasticizers, inorganic or organic pigments anddyes (for example, pigment or dye colorants different from theopacifying colorants described below), flame retardants, antimicrobials,fungicides, preservatives, pH buffers, optical brighteners, tintingcolorants, metal particles such as metal platelets or metal flakes,thickeners, and inorganic fillers (such as clays) that are not any ofthe other additive materials or opacifying colorants described herein,all of which additives are described in more detail above. The amountsare based on the total weight of the dry foamed composition. As notedabove, most embodiments include at least one surfactant that is afoaming agent and at least one foam stabilizing agent.

Particularly useful one or more (c) additives comprise two or morematerials selected from a foaming agent, a foam stabilizing agent, atinting colorant, an optical brightener, a flame retardant, anantimicrobial agent, and an inorganic filler (such as a clay).

Thus, the foamed, opacifying element can comprise one or more tintingcolorants as (c) additives in the dry foamed composition in an amount ofat least 0.0001 weight % and up to and including 3 weight %, based onthe total weight of the dry foamed composition. Such tinting colorant(s)can be present in at least the porous particles, and can be elsewherealso.

It is also useful to include one or more optical brighteners as (c)additives in an amount of at least 0.001 weight % and up to andincluding 0.4 weight %, based on the total weight of the dry foamedcomposition.

The dry foamed composition is “substantially” dry in nature, meaningthat it comprises less than 5 weight %, or even less than 2 weight %, ofaqueous medium (including water and any other solvents), based on thetotal weight of the dry foamed composition. This amount may not includeany water that can be present in the discrete pores of the porousparticles. The dry foamed composition in the dry opacifying layergenerally comprises at least 90% solids, or at least 95% solids, or evenat least 98% solids.

The dry foamed composition can also contain at least 0.002 weight %, oreven at least 0.02 weight % and up to and including 2 weight % or up toand including 1 weight %, of one or more (e) opacifying colorants (asdescribed above), which opacifying colorants absorb all wavelengths ofthe predetermined electromagnetic radiation (as defined above). Detailsof such opacifying colorants are described above, and the amounts arebased on the total weight of the dry foamed composition. Such opacifyingcolorants can be present within the (a) porous particles or within the(b) binder material, or within both (a) and (b) components.

In some embodiments, a carbon black is present as the (e) opacifyingcolorant in an amount of at least 0.002 weight % and up to and including1 weight %, based on the total weight of the dry foamed composition.

In many embodiments of the foamed, opacifying element, the opacifyingcolorant (such as a carbon black) can be present within: the continuouspolymeric phase of the porous particles; a volume of the first set (oradditional set) of discrete pores; or both the volume of the first set(or additional set) of discrete pores and the continuous polymeric phaseof the porous particles.

The foamed, opacifying elements are designed particularly to have asingle dry opacifying layer with the components disposed on the poroussubstrate so that the single dry opacifying layer in a given elementexhibits a light blocking value of at least 4 or more likely at least 5.For this purpose, light blocking value can be determined as describedabove.

In addition, such dry opacifying layers exhibit a luminous reflectance(opacity) that is greater than 40%, as measured for the Y tristimulusvalue. For this purpose, luminous reflectance (brightness) is determinedas described above.

Dry porous substrates useful in the practice of the present inventioncan comprise various porous materials such as woven and nonwoven textilefabrics composed of nylon, polyester, cotton, aramide, rayon,polyolefin, acrylic wool, porous glasses, fiberglass fabrics, or felt ormixtures thereof, or porous polymeric films [such as porous filmsderived from triacetyl cellulose, polyethylene terephthalate (PET),diacetyl cellulose, acetate butyrate cellulose, acetate propionatecellulose, polyether sulfone, polyacrylic based resin, for example,poly(methyl methacrylate), a polyurethane-based resin, polyester,polycarbonate, aromatic polyamide, polyolefins (for example,polyethylene and polypropylene), polymers derived from vinyl chloride(for example, polyvinyl chloride and a vinyl chloride/vinyl acetatecopolymer), polyvinyl alcohol, polysulfone, polyether, polynorbornene,polymethylpentene, polyether ketone, (meth)acrylonitrile], porous paperor other porous cellulosic materials, canvases, porous wood, porousplaster and other porous materials that would be apparent to one skilledin the art. The porous substrates can vary in dry thickness as long asthey are suitable for the desired foamed, opacifying element. In mostembodiments, the dry porous substrate thickness is at least 50 μm.

Particularly useful porous substrates comprise a porous textile web(such as a flexible porous textile web), a porous polymer film (such asa woven polyester fabric), a porous cellulosic material (such as porouspapers), a porous ceramic material, or a porous glass material.

The porous substrates can be surface treated by various processesincluding corona discharge, glow discharge, UV or ozone exposure, flame,or solvent washing in order to promote desired physical properties.

Generally, the foamed opacifying elements according to this inventionare designed with a single dry opacifying layers disposed on one or bothsupporting (planar) sides of the porous substrate as described above. Inmany useful embodiments, a single dry opacifying layer is disposed ononly one supporting sides of the porous substrate using techniquesdescribed below, and in such embodiments, the dry opacifying layer canbe the only (outermost) layer disposed on the porous substrate.

In other embodiments, a dry opacifying layer can be disposed or formedon one or both supporting sides of a porous substrate, which dryopacifying layer can be formed using a foamable aqueous composition thatis designed according to the present invention. In such embodiments, adry non-opacifying layer can be disposed on the single dry opacifyinglayer (on one or both supporting sides of the porous substrate). Suchdry non-opacifying layer can be designed with any of the components (a)through (c), but it does not comprise an (e) opacifying colorant asdefined herein. Examples of useful dry non-opacifying layers can bedesigned to have various functions such as surface protection,antimicrobial properties, and color modification.

Attractive finishes can be imparted to the foamed, opacifying element byfor example, flocking the foamed aqueous composition that is disposed onthe porous substrate. Flock or very short (0.2 mm and up to several mm)fibers can be disposed in the foamed aqueous composition using either byelectrostatic or mechanical techniques on the outermost surface of thefoamed aqueous composition before or during drying.

Method of Making Foamed, Opacifying Elements

The foamed, opacifying elements are prepared by firstly providing afoamable aqueous composition as described above comprising essentialcomponents (a) through (e) in the described amounts.

This foamable aqueous composition is then aerated to provide a foamedaqueous composition having a foam density of at least 0.1 g/cm³ and upto and including 0.5 g/cm³, or of at least 0.15 g/cm³ and up to andincluding 0.4 g/cm³. This aeration procedure can be carried out usingany suitable conditions and equipment that would be readily apparent toone skilled in the art in order to create a “foam” in the presence of afoaming agent as the (c) additive surfactant described above. Forexample, aeration can be carried out by mechanically introducing air oran inert gas (such as nitrogen or argon) in a controlled manner. Highshear mechanical aeration can be carried out using sonication or highspeed mixers, such as those equipped with a cowles blade, or withcommercially available rotorstator mixers with interdigitated pins suchas an Oakes mixer or a Hobart mixer, by introducing air under pressureor by drawing atmospheric air into the foamable aqueous composition bythe whipping action of the mixer. Suitable foaming equipment can be usedin a manner to provide the desired foam density with modestexperimentation. It can be useful to chill or cool the foamable aqueouscomposition below ambient temperature to increase its stability byincreasing its viscosity, and to prevent collapse of the foamableaqueous composition. This chilling operation can be carried outimmediately before, after, or during the aeration procedure. Stabilityof the foamed aqueous composition can also be enhanced by the presenceof a foam stabilizing agent as another of the (c) additives.

Once the foamed aqueous composition has been formed, it can be disposedonto one or more supporting sides (or planar surfaces) of a suitableporous substrate (described above). This procedure can be carried out inany suitable manner that does not undesirably diminish the foam density(or foam structure) of the foamed aqueous composition. For example, aplanar surface of the porous substrate can be coated with the aqueousfoamed composition using any suitable known coating equipment (floatingknife, hopper, blade, or gap) and coating procedures including but notlimited to blade coating, gap coating, slot die coating, X-slide hoppercoating, or “knife-over-roll” operation, especially if multiple layersare applied to the substrate. If the dry opacifying layer is the onlylayer to be formed on the substrate, the foamed aqueous composition canbe applied using blade coating, gap coating, slot die coating, or“knife-over-roll” coating. For example, useful layer forming (coating)means are described in U.S. Pat. No. 4,677,016 (Ferziger et al.), thedisclosure of which is incorporated herein by reference.

Thus, the foamed aqueous composition can be disposed directly onto anouter surface of the porous substrate (“directly” means no interveningor intermediate layers) such as a porous woven cloth fabric, afiberglass fabric, or cellulosic material.

When multiple layers are to be disposed on the porous substrate, asingle dry opacifying layer can be disposed on the porous substrate andan outermost non-opacifying layer can be disposed on the dry opacifyinglayer using a suitable coating means as described above.

Once each foamed aqueous composition has been disposed on a planarsurface of the porous substrate, it is generally dried to become“substantially” dry (to be defined in relation to the amount of waterthat is present, as described above for the dry foamed composition), andat least partially cured (meaning the one or more binder materials areat least partially cured or crosslinked), simultaneously or in anyorder, to provide a dry foamed composition (and dry opacifying layer) oneither or both supporting sides of the porous substrate (preferably ononly one supporting side of the porous substrate). Drying and at leastpartial curing can be accomplished by any suitable means such as byheating with warm or hot air, microwaves, or IR irradiation at atemperature and time sufficient for at least drying and at least partialcuring (for example, at less than 180° C.). Curing the binder materialscan be promoted by heat or radiation or other conditions to which thebinder materials are responsive for crosslinking. In some embodiments, asuitable functionalized latex composition is used as the bindermaterial. Upon heating, the binder material(s) dries, and a possiblecuring or crosslinking reaction taking place between reactive sidegroups of suitable curable polymer chains. If the particular bindermaterial is not itself heat reactive, suitable catalysts or curing(crosslinking) agents can be added to the foamable aqueous compositionto promote curing or crosslinking.

After drying and at least partially curing, the dry foamed compositionon the porous substrate is then crushed or densified on the poroussubstrate to form a dry opacifying layer in the foamed, opacifyingelement. This process can be carried out in any suitable manner but itis generally carried out by a process that provides pressure to the dryfoamed composition on the porous substrate, for example, by passing theporous substrate with the dry foamed composition through a compressioncalendering operation, pressing operation, or embossing operation, or acombination thereof. For example, the coated porous substrate can bepassed through a combination of calendering and embossing rollers toreduce the thickness of the dry foamed composition and to densify thefoam in the dry foamed composition. The thickness of the dry foamedcomposition can be reduced by at least 20% during such an operation.This process of crushing the dry foamed composition can be considered a“densifying operation” as the dry foamed composition is made denserwhile it is pressed together on the porous substrate. The thickness ofthe dry foamed composition before and after crushing (densifying) can bedetermined by a known technique such as laser profilometry. After dryingand crushing, the foamed, opacifying element according to the presentinvention generally has a light blocking value of at least 4, or atleast 5, which LBV is determined as described above.

It is also possible to provide an embossed design on the outermostlayer, for example, the dry opacifying layer or dry non-opacifyinglayer, of the foamed, opacifying element during the densifying operationsuch as for example, by patterned embossing or calendering the dryoutermost layer, to create selected regions of high or low opacity andthickness. The resulting embossed design can be viewed from either sidein transmission.

It is further possible to print images on the outer surface of theoutermost layer, such as the dry opacifying layer or dry non-opacifyinglayer of the foamed, opacifying element or on the backside of the poroussubstrate, or on both, using any suitable printing means such as inkjetprinting or flexographic printing, thereby forming printed images oftext, pictures, symbols, other objects, or combinations thereof. Suchprinted images can be visible, or they can invisible to the unaided eye(for example, using fluorescent dyes in the printed images).Alternatively, the outermost layer can be covered by printing or othermeans, with a colorless layer to provide a glossy finish.

The crushing or densifying process described above can be carried out atany suitable temperature including room temperature (for example, 20°C.) and up to and including 90° C., or more likely at a temperature ofat least 20° C. and up to and including 80° C.

After densifying the dry foamed composition in the dry opacifying layer,the dry opacifying layer can be subjected to conditions that promotefurther curing such as those conditions that are described above for theinitial drying/curing operations.

The present invention provides at least the following embodiments andcombinations thereof, but other combinations of features are consideredto be within the present invention as a skilled artisan would appreciatefrom the teaching of this disclosure:

1. A method for providing a foamed, opacifying element, the methodcomprising:

providing a foamable aqueous composition that has at least 35% solidsand up to and including 70% solids, and comprises:

(a) at least 0.05 weight % and up to and including 15 weight % of porousparticles, each porous particle comprising a continuous polymeric phaseand a first set of discrete pores dispersed within the continuouspolymeric phase, the porous particles having a mode particle size of atleast 2 μm and up to and including 50 μm and a porosity of at least 20volume % and up to and including 70 volume %, and the continuouspolymeric phase having a glass transition temperature greater than 80°C. and comprising a polymer having a viscosity of at least 80centipoises and up to and including 500 centipoises at a shear rate of100 sec⁻¹ in ethyl acetate at a concentration of 20 weight % at 25° C.;

(b) at least 20 weight % of a binder material;

(c) at least 0.0001 weight % of one or more additives comprising asurfactant;

(d) water;

(e) at least 0.001 weight % of an opacifying colorant different from allof the (c) additives, which opacifying colorant absorbs predeterminedelectromagnetic radiation,

all amounts based on the total weight of the foamable aqueouscomposition;

aerating the foamable aqueous composition to provide a foamed aqueouscomposition having a foam density of at least 0.1 g/cm³ and up to andincluding 0.5 g/cm³;

disposing the foamed aqueous composition onto a surface of at least onesupporting side of a porous substrate;

drying and at least partially curing, simultaneously or in any order,the foamed aqueous composition to provide a dry foamed composition; and

densifying the dry foamed composition to provide a dry opacifying layerin a foamed, opacifying element.

2. The method of embodiment 1, further comprising:

after densifying the dry foamed composition, further curing the dryopacifying layer.

3. The method of embodiment 1 or 2, comprising:

aerating the foamable aqueous composition by introducing air or an inertgas into the foamable aqueous composition in a controlled manner.

4. The method of any of embodiments 1 to 3, further comprising:

cooling the foamable aqueous composition below ambient temperatureduring aerating.

5. The method of any of embodiments 1 to 4, comprising:

disposing the foamed aqueous composition on the surface using a coatingprocess. 6. The method of any of embodiments 1 to 5, comprising:

densifying the dry foamed composition on the surface by a compressioncalendaring operation, pressing operation, or embossing operation, or acombination thereof.

7. The method of any of embodiments 1 to 6, comprising:

aerating the foamable aqueous composition to provide a foamed aqueouscomposition having a foam density of at least 0.15 g/cm³ and up to andincluding 0.4 g/cm³.

8. The method of any of embodiments 1 to 7, wherein the continuouspolymeric phase of the porous particles comprises at least 70 weight %,based on the total polymer weight in the continuous polymeric phase, ofone or more polymers derived from one or more of cellulose acetate,cellulose butyrate, cellulose acetate butyrate, and cellulose acetatepropionate.

9. The method of any of embodiments 1 to 8, wherein the dry opacifyinglayer is the only layer disposed on the porous substrate.

10. The method of any of embodiments 1 to 9, further comprising:

disposing a non-opacifying layer on the opacifying layer.

11. The method of embodiment 10, wherein the foamed aqueous compositionand the non-opacifying layer are disposed on the porous substrate usinga blade coating, gap coating, slot die coating, X-slide hopper coating,or knife on roll operation. 12. The method of any of embodiments 1 to11, wherein the dry opacifying layer is the only layer on the substrate,and is disposed as the foamed aqueous composition using a blade coating,gap coating, slot die coating, or knife on roll operation.

13. The method of any of embodiments 1 to 12, wherein the opacifyingcolorant in the foamable aqueous composition is a carbon black that ispresent in an amount of at least 0.003 weight % and up to and including0.2 weight %, based on the total weight of the foamable aqueouscomposition.

14. The method of any of embodiments I to 13, wherein the foamableaqueous composition comprises at least 0.5 weight % and up to andincluding 10 weight % of the porous particles that have a mode particlesize of at least 3 μm and up to and including 30 μm, based on the totalweight of the foamable aqueous composition.

15. The method of any of embodiments 1 to 14, wherein the porousparticles in the foamable aqueous composition have a mode particle sizeof at least 3 μm and up to and including 20 μm.

16. The method of any of embodiments 1 to 15, wherein the foamableaqueous composition has at least 40% solids and up to and including 60%solids, and wherein:

the continuous polymeric phase comprises at least 70 weight % and up toand including 100 weight %, based on the total polymer weight in thecontinuous polymeric phase, of one or more polymers derived from one ormore of cellulose acetate, cellulose butyrate, cellulose acetatebutyrate, and cellulose acetate propionate;

the porous particles are present in an amount of at least 0.5 weight %and up to and including 10 weight %;

the binder material is present in an amount of at least 30 weight % andup to and including 50 weight % and has a glass transition temperatureof less than 25° C.;

the one or more (c) additives further comprise an optical brightener inan amount of at least 0.01 weight % and up to and including 2 weight %;and

carbon black is present as at least one opacifying colorant in an amountof at least 0.003 weight % and up to and including 0.2 weight %,

all amounts being based on the total weight of the foamable aqueouscomposition.

17. The method of any of embodiments 1 to 16, wherein the one or more(c) additives of the foamable aqueous composition further comprise anoptical brightener that is present within: the continuous polymericphase of the porous particles; a volume of the first set of discretepores; or both the volume of the first set of discrete pores and thecontinuous polymeric phase of the porous particles.

18. The method of any of embodiments 1 to 17, wherein the at least one(c) additives of the foamable aqueous composition further comprise metalflakes that are present within the porous particles.

19. The method of any of embodiments 1 to 18, wherein the surfactant ofthe one or more (c) additives in the foamable aqueous composition is afoaming agent and the one or more (c) additives further comprise a foamstabilizing agent.

20. The method of any of embodiments 1 to 19, wherein the one or more(c) additives of the foamable aqueous composition further comprise atinting colorant that is present in an amount of least 0.0001 weight %and up to and including 3 weight %, based on the total weight of thefoamable aqueous composition.

21. The method of any of embodiments 1 to 20, wherein the one or more(c) additives of the foamable aqueous composition comprise an opticalbrightener in an amount of at least 0.01 weight % and up to andincluding 2 weight %, based on the total weight of the foamable aqueouscomposition.

22. The method of any of embodiments 1 to 21, wherein the one or more(c) additives of the foamable aqueous composition comprise two or morematerials selected from a foaming agent, a foam stabilizing agent, atinting colorant, an optical brightener, a flame retardant, anantimicrobial agent, and an inorganic filler.

23. The method of any of embodiments 1 to 22, wherein the one or more(c) additives of the foamable aqueous composition comprise anantimicrobial agent comprising silver metal, a silver-containingcompound, copper metal, a copper-containing compound, or a mixture ofany of these.

24. The method of any of embodiments 1 to 23, wherein the dry opacifyinglayer of the foamed, opacifying element has a light blocking value of atleast 4 and a luminous reflectance of luminous reflectance that isgreater than 40% as measured for the Y tristimulus value.

The following Examples are provided to illustrate the practice of thisinvention and are not meant to be limiting in any manner. The followingmaterials were used in the Examples.

Materials used in the Following Examples:

The continuous polymeric phase polymers used in the following exampleswere the Eastman™ Cellulose Acetate Butyrate 381-0.5 (CAB), a celluloseester, T_(g) of 130° C. (obtained from Chem Point); and Kao KBT-382,T_(g) of 60° C., a bis-phenol type polyester [obtained from KaoSpecialties Americas LLC, a part of Kao Corporation (Japan)].

NALCO® 1060 containing colloidal silica was obtained from Nalco ChemicalCompany as a 50 weight % aqueous dispersion.

The poly(methylamino ethanol adipate) (AMAE) co-stabilizer was preparedusing known procedures and starting materials.

Carboxy methylcellulose (CMC, 250,000 kDa) was obtained from AcrosOrganics or from Ashland Aqualon as Aqualon 9M31F. These products wereused interchangeably.

The amphiphilic block copolymer of polyethylene oxide andpolycaprolactone (PEO-b-PCL) 5K-20K, was prepared using the proceduredescribed in U.S. Pat. No. 5,429,826 (Nair et al.) where the firstnumber is the molecular weight of the hydrophilic block segment, PEO,and the second number is the molecular weight of the oleophilic blocksegment, PCL.

TERGITOL® 15-S-7, a C12-C14 secondary alcohol surfactant having an HLBvalue of 12.4, was obtained from the Dow Chemical Corp.

The optical brightener TINOPAL® OB CO was obtained from BASFCorporation.

The porous substrates used in the Examples below were various porouswoven fabrics, porous polyester materials, and porous cotton materials,all having a weight of approximately 80-110 g/m².

The carbon black (K) opacifying colorant used as an aqueous dispersionwas Regal 330 (Cabot Corp.) that was hydrophobically surface modified.

The yellow (Y1) tinting colorant, Pigment Yellow 83 (Monolite DiarylideYellow HR) was obtained from Heubach, Heucotech Ltd.

The yellow (Y2) tinting colorant, Pigment Yellow 3 (Hansa Yellow 3) wasobtained from Lansco Colors.

The cyan (C) tinting colorant, Pigment Blue 15:3 (Sunfast Blue 15:3) wasobtained from Sun Chemical.

The magenta (M) pigment, Pigment Red 185 (Graphtol Carmine HF4C) wasobtained from Clariant.

DISPERBYK® 190, a copolymer derived from polystyrene, polypropyleneglycol, and polyethylene glycol, was obtained from BYK-Chemie USA.

SOLSPERSE® 43000, a polyacrylate polymeric dispersant, was obtained fromLubrizol Corp.

EAGLETEX® C-3018 and EAGLEBAN® FRC-0307 Drapery Compounds were obtainedfrom Eagle Performance Products, where the binder material was aself-crosslinking terpolymer derived from acrylonitrile, n-butylacrylate, and ethyl acrylate and having a glass transition temperatureof −10° C.

Measurements:

The mode particle size of the porous particles used in the Examples wasmeasured using a Sysmex FPIA-3000 automated particle size analyzer fromMalvern Instruments. The particle size of the dispersed pigments wasdetermined using light scattering.

The porosity of the porous particles was measured using the knownmercury intrusion porosimetry method.

The light blocking ability of each foamed, opacifying element in theExamples, in transmitted light, was evaluated by measuring its lightblocking value (LBV) using a custom-built apparatus consisting of afiber optic Xenon light source, a computer controlled translationalstage and an optical photometer. The fiber optic was positioned 10 mmabove the surface of the fabric. A photo detector was placed on theother side of the sample element directly under the fiber optic in orderto quantify the amount of light that passed through the sample element.The light blocking value of each sample was calculated by comparing thelight intensity (I) that passed through the sample element to the lightintensity (I₀) that reached the detector when no sample element waspresent, and using the equation:

−log₁₀(I/I₀).

The luminous reflectance (or brightness) of each sample element wasdetermined by first measuring the spectral reflectance in the 400-700 nmwavelength range using a Hunter Labs UltraScan XE colorimeter equippedwith an integrating sphere and a pulsed Xenon light source. A light trapand a standard white tile were used to fix the reflectance range from 0to 100%. The X, Y, and Z tristimulus values of each dry opacifying layerwere also determined and used in conjunction with the CIELab color space(standard D65 illuminant) to calculate specific values for the lightness(L*), red-green character (a*), and yellow-blue character (b*) of eachdry opacifying layer. The Y tristimulus value was used as a measure ofthe luminous reflectance or “brightness” of each sample.

Preparation of Pigment Dispersions for Porous Particles:

All pigment (opacifying colorants and tinting colorants) dispersionswere prepared by combining dry pigment, a dispersant, and a liquid in asuitable milling vessel. The particle size of each pigment was reducedby milling it using ceramic media until all pigment particles werereduced below a diameter of 1 μm as determined by optical microscopy.The dispersions were further diluted in the same liquid medium forincorporation into porous particles or foamed aqueous composition. Thedispersions varied in the type of pigment, dispersant and dispersantlevel relative to pigments shown below in TABLE I. Dv is the volumeweighted mean diameter, in nanometers. In TABLE I, the Dispersion isidentified by the pigments (K, Y1, Y2, C, or M).

TABLE I Dispersions Dispersant (weight % of Pigment Dispersion PigmentPigment) Weight % Dv (nm) D-K K SOLSPERSE ® 10.72 101 43000 (25) D-Y1 Y1SOLSPERSE ® 8.60 247 43000 (20) D-Y2 Y2 SOLSPERSE ® 16.83 289 43000 (20)D-C C SOLSPERSE ® 19.08 139 43000 (30) D-M M Disperbyk ® 190 15.12 289(20)

Preparation of Porous Particles:

The various porous particles used for preparing a foamed, opacifyingelement for each Invention Example and Comparative Example are describedbelow and TABLE II below summarizes the characteristics of theparticles. All of the porous particles contained 1 weight % of opticalbrightener in the continuous polymeric phase.

P1 Porous Particles Containing 1 weight % Opacifying Colorant (K) in theDiscrete Pores and Kao KBT382 in Continuous Polymeric Phase

An aqueous phase was made up by dissolving 68.2 grams of CMC in 3450grams of distilled water and adding to 134 grams of the D-K dispersioncontaining 18.6 weight % of the surface modified carbon black. Thisaqueous phase was dispersed in 11,363 grams of an oil phase containing2,475 grams of Kao KBT382 polyester and 25 grams of the opticalbrightener, TINOPAL® OB CO in ethyl acetate using a homogenizer. Theresulting water-in-oil emulsion was dispersed using the Silverson L4Rhomogenizer for two minutes at 1200 RPM, in 54,338 grams of a 200 mmolarpH 4 acetate buffer containing 3,050 grams of NALCO® 1060 colloidalsilica, followed by homogenization in an orifice homogenizer at 1000 psi(70.4 kg_(f)/cm²) to form a water-in-oil-in-water double emulsion. Theethyl acetate was removed under reduced pressure at 40° C. afterdilution of the water-in-oil-in-water emulsion with an equal weight ofwater. The resulting suspension of solidified porous particles wasfiltered and the P1 porous particles were washed with water severaltimes, followed by rinsing with a 0.1 weight % solution of TERGITOL®15-S-7 surfactant. The isolated P1 porous particles were then air dried.Typically, the discrete pores contained within the porous particlesprepared according to this procedure had an average diameter of from 150nm and up to and including 1,500 nm.

P2 Porous Particles Containing 1 weight % Yellow Pigment (Y1) in theDiscrete Pores and 1 weight % Optical Brightener in Continuous PolymericPhase Cellulose Acetate Butyrate to Provide Tinting Colorant

An aqueous phase was made up by dissolving 5 grams of CMC in 240.5 gramsof distilled water and adding to 11.6 grams of the D-Y1 dispersioncontaining 8.6 weight % of PY83. This aqueous phase was dispersed in831.8 grams of an oil phase containing 97.7 grams of CAB, 2 grams ofPEO-PCL and 1 gram of the optical brightener, TINOPAL® OB CO in ethylacetate using a homogenizer. A 975-gram aliquot of the resultingwater-in-oil emulsion was dispersed using the Silverson L4R homogenizerfor two minutes at 1200 RPM, in 1625 grams of a 200 mmolar pH 4 acetatebuffer containing 39 grams of NALCO® 1060 colloidal silica, and 9.75grams of AMAE co-stabilizer followed by homogenization in an orificehomogenizer at 1000 psi (70.4 kg_(f)/cm²) to form awater-in-oil-in-water double emulsion. The ethyl acetate was removed,and the resulting P2 porous particles were washed and isolated asdescribed for P1

P3 Porous Particles Containing 1 weight % Opacifying Colorant (K) in theDiscrete Pores and 1 weight % Optical Brightener in Continuous PolymericPhase Cellulose Acetate Butyrate

The P3 porous particles were prepared as described for the P2 porousparticles except that the D-K dispersion was used in place of the D-Y1dispersion.

P4 Porous Particles Containing 5 weight % Yellow Pigment (Y2) in theDiscrete Pores and 1 weight % Optical Brightener in Continuous PolymericPhase Cellulose Acetate Butyrate

The P4 porous particles were prepared as described for the P2 porousparticles except that the D-Y2 dispersion was used in place of the D-Y1dispersion.

P5 Porous Particles Containing 5 weight % Cyan Pigment (C) in theDiscrete Pores and 1 weight % Optical Brightener in Continuous PolymericPhase Cellulose Acetate Butyrate

The P5 porous particles were prepared as described for the P2 porousparticles except that the D-C dispersion was used in place of the D-Yldispersion.

P6 Porous Particles Containing 5 weight % Magenta Pigment (M) in theDiscrete Pores and 1 weight % Optical Brightener in Continuous PolymericPhase Cellulose Acetate Butyrate

The P6 porous particles were prepared as described for the P2 porousparticles except that the D-M dispersion was used in place of the D-Y1dispersion.

P7 Porous Particles Containing 0.8 weight % Opacifying Colorant (K) inthe Discrete Pores and 1 weight % Optical Brightener in ContinuousPolymeric Phase Cellulose Acetate Butyrate

The P7 porous particles were prepared as described for the P3 porousparticles except that the amount of the D-K dispersion used was lower toobtain the desired level of K in the porous particles.

P8 Porous Particles Containing No Opacifying Colorant and 1 weight %Optical Brightener in Continuous Polymeric Phase Cellulose AcetateButyrate

The P8 porous particles were prepared as described for the P2 porousparticles except that no pigment dispersion was used in the preparation.

TABLE II Porous Particle size Porosity Particles Features (μm) (Vol %)P1 1 weight % K in discrete pores and 4.5 28 continuous polymeric phaseKao KBT382 P2 1 weight % Yellow Pigment (Y1) 5.9 56 in the discretepores and continuous polymeric phase CAB to provide tinting colorant P31 weight % K in discrete pores and 6.8 57 continuous polymeric phase CABP4 5 weight % Yellow Pigment (Y2) 5.7 52 in the discrete pores andcontinuous polymeric phase CAB to provide tinting colorant P5 1 weight %Cyan Pigment (C) in 6.8 52 the discrete pores and continuous polymericphase CAB to provide tinting colorant P6 1 weight % Magenta Pigment (M)5.7 57 in the discrete pores and continuous polymeric phase CAB toprovide tinting colorant P7 0.8 weight % K in discrete pores 6.6 49 andcontinuous polymeric phase CAB P8 no opacifying colorant and in 7.6 54continuous polymeric phase CAB

Preparation of Foamable Aqueous Compositions; Foamed AqueousCompositions; and Foamed, Opacifying Elements:

In general, each foamable aqueous composition was made by incorporatingthe appropriate porous particles in either a 48 weight % solidsEAGLETEX® C-3018 Drapery Compound or a 55 weight % solids EAGLEBAN®FRC-0307 Drapery Compound. For each foamed aqueous composition, thedrapery compound was added to an appropriately sized container. Porousparticles in the various examples were dispersed into the mixture bystirring at 1200 rev/minute with a 50 mm diameter Cowles blade atambient temperature for 30-60 minutes. Each of the resulting dispersions(foamable aqueous composition) was used to prepare a foamed aqueouscomposition under pressure using an Oakes 2M Laboratory Mixer Model2MBT1A. Each resulting foamed aqueous composition, having a density offrom 0.20 g/cm³ to 0.25 g/cm³, was coated onto a surface of the poroussubstrate described above with a coating knife, dried at a temperatureof from 120° C. to 160° C. as described in the Examples below until themoisture content was less than 2 weight %, and crushed (“densified”) onthe porous substrate between hard rollers under pressure.

COMPARATIVE EXAMPLE 1

A comparative foamable aqueous composition was prepared from 950 gramsof EAGLETEX® C-3018 Drapery Compound and 50 grams of a 60.54% weight %aqueous dispersion of P1 porous particles. The resulting foamableaqueous composition was foamed (aerated) and coated onto a surface ofthe porous substrate described above with a coating knife with a 2.794mm (0.110 inch) gap. The coating was dried at 120° C. for 10 minutes ina forced air oven. The resulting dry foamed layer (dry opacifying layer)in the resulting dry foamed, opacifying element contained 6.11 weight %of the P1 porous particles, 0.0611 weight % of carbon black, and 0.146g/m² of carbon black on a dry weight basis. The LBV of the dryopacifying layer was 4; the layer had a weight of 238 g/m², and aluminous reflectance of 48.

COMPARATIVE EXAMPLE 2

Another comparative foamable aqueous composition was prepared from 1000grams of EAGLETEX® C-3018 Drapery Compound. No porous particles wereincluded. The foamable aqueous composition was foamed (aerated) andcoated onto a surface of the porous substrate described above with acoating knife with a 2.54 mm (0.100 inch) gap in a pilot coating machineat 1 m/min and dried at 160° C. The resulting dry foamed composition ofthe resulting foamed, opacifying element did not contain porousparticles or carbon black or another opacifying colorant. Although theluminous reflectance was 86 of the foamed, opacifying element, its LBVwas only 2 for the dry opacifying layer having a weight of 278 g/m² andthe element therefore was not sufficiently light-blocking.

COMPARATIVE EXAMPLE 3

Still another comparative foamable aqueous composition was prepared fromof 936.65 grams of EAGLETEX® C-3018 Drapery Compound and 63.35 grams ofa 52.11 weight % dispersion of the P8 porous particles. The resultingfoamable aqueous composition was foamed (aerated) and coated onto asurface of the porous substrate described above with a coating knifewith a 2.54 mm (0.100 inch) gap as described in Comparative Example 2.The resulting dry foamed composition of the resulting foamed, opacifyingelement contained 6.71 weight % the P8 porous particles but there was nocarbon black or other opacifying colorant. Although the luminousreflectance was 80, the LBV of the element was only 2 for the dryopacifying layer weight of 190 g/m² and therefore the foamed, opacifyingelement was not sufficiently light-blocking.

INVENTION EXAMPLE 1

A foamable aqueous composition according to the present invention wasprepared from 940.3 grams of EAGLETEX® C-3018 Drapery Compound and 59.7grams of a 49.76 weight % aqueous dispersion of the P3 porous particles.This foamable aqueous composition was foamed (aerated) to provide afoamed aqueous composition according to the present invention, which wascoated onto a surface of the porous substrate described above with acoating knife with a 2.794 mm (0.110 inch) gap. The coating was dried asdescribed in Comparative Example 1. The dry foamed composition (dryopacifying layer) contained 6.10 weight % of the P3 porous particles,0.0610 weight % of carbon black, and 0.136 g/m² of carbon black on a dryweight basis. The resulting foamed, opacifying element exhibited an LBVof 5 for the dry opacifying layer weight of 223 g/m², which wassignificantly more opacifying than the foamed, opacifying element ofComparative Example 1. The inventive foamed, opacifying element was alsobrighter in appearance given the higher luminous reflectance value of 53compared to that of Comparative Example 1. These advantages of InventionExample 1 are due to the higher T_(g) of cellulose acetate butyratematerial used as the continuous polymeric phase of the porous particlesand its ability to survive high temperature drying without losing thelight scattering property of the pores in the porous particles,improving both brightness and, in conjunction with the carbon blackopacifying colorant, the opacity.

INVENTION EXAMPLE 2

A foamable aqueous composition according to the present invention wasprepared with 1399.8 grams of EAGLETEX® C-3018 Drapery Compound and100.2 grams of a 49.25 weight % aqueous dispersion of the P7 porousparticles. This foamable aqueous composition was foamed (aerated) andthe foamed aqueous composition according to the present invention coatedonto a surface of the porous substrate described above with a coatingknife with a 2.54 mm (0.100 inch) gap as described in ComparativeExample 2. The dry foamed composition (dry opacifying layer) in thefoamed, opacifying element according to this invention contained 6.71weight % of the P7 porous particles, 0.0557 weight % of carbon black,and 0.136 g/m² of carbon black on a dry weight basis. This inventivefoamed, opacifying element exhibited an LBV of 5.8 for the dryopacifying layer weight of 244 g/m², and it had a luminous reflectancevalue of 52.

INVENTION EXAMPLE 3

A foamable aqueous composition according to the present invention wasprepared with 1,388.3 grams of EAGLETEX® C-3018 Drapery Compound, 100.2grams of a 49.25 weight % aqueous dispersion of the P7 porous particles,and 11.5 grams of a 49.22 weight % aqueous dispersion of the P2 porousparticles. This aqueous foamable composition was foamed (aerated) andthe resulting foamed aqueous composition according to this invention wascoated onto a surface of the porous substrate described above with acoating knife with a 2.54 mm (0.100 inch) gap as described inComparative Example 2. The dry foamed composition (dry opacifying layer)in the foamed, opacifying element according to this invention contained7.49 weight % of the P7 and P2 porous particles, 0.0557 weight % ofcarbon black, 0.0078 weight % of yellow pigment Y1, and 0.137 g/m² ofcarbon black on a dry weight basis. This inventive foamed, opacifyingelement exhibited an LBV of 5.9 for a dry opacifying layer weight of 246g/m², and a luminous reflectance value of 52, the same as for InventionExample 2 but this Invention Example 3 foamed, opacifying element alsoexhibited a yellow tinted appearance that was reflected in the b* valueof 0.46.

INVENTION EXAMPLE 4

A foamable aqueous composition according to the present invention wasprepared with 1,388.9 grams of EAGLETEX® C-3018 Drapery Compound, 100.2grams of a 49.25 weight % aqueous dispersion of the P7 porous particles,and 10.9 grams of a 52.39 weight % aqueous dispersion of the P5 porousparticles. This composition was foamed (aerated) and the resultingfoamed aqueous composition was coated onto a surface of the poroussubstrate described above with a coating knife with a 2.54 mm (0.100inch) gap as described in Comparative Example 2. The dry foamedcomposition (dry opacifying layer) in the foamed, opacifying elementaccording to this invention contained 7.48 weight % of the P7 and P5porous particles, 0.0557 weight % of carbon black, 0.0078 weight % ofcyan pigment C, and 0.135g/m² of carbon black on a dry weight basis.This inventive foamed, opacifying element exhibited an LBV of 6 for thedry opacifying layer weight of 242 g/m², and a luminous reflectancevalue of 51.5, similar to that of Invention Example 2 but InventionExample 4 also exhibited a cyan tinted appearance that was reflected inthe b* value of −1.82.

INVENTION EXAMPLE 5

A foamable aqueous composition according to the present invention wasprepared with 926.0 grams of EAGLETEX® C-3018 Drapery Compound, 66.8grams of a 49.25 weight % aqueous dispersion of the P7 porous particles,and 7.2 grams of a 53.46 weight % aqueous dispersion of the P6 porousparticles. This composition was foamed (aerated) and the resultingfoamed aqueous composition was coated onto a surface of the poroussubstrate described above with a coating knife with a 2.54 mm (0.100inch) gap as described in Comparative Example 2. The dry foamedcomposition of the foamed, opacifying element according to thisinvention contained 7.49 weight % of the P7 and P6 porous particles,0.0557 weight % of carbon black, 0.0078 weight % of magenta pigment Mand 0.111 g/m² of carbon black on a dry weight basis. This inventivefoamed, opacifying element exhibited an LBV of 5.3 for a dry opacifyinglayer weight of 199 g/m², and a luminous reflectance value of 52, thesame as for Invention Example 2 but it also exhibited a magenta tintedappearance that was reflected in the a* value of 1.19 and b* value of−1.31.

INVENTION EXAMPLE 6

A foamable aqueous composition was prepared according to the presentinvention with 868.9 grams of EAGLEBAN® FRC-0307 Drapery Compound and131.12 grams of a 49.25 weight % aqueous dispersion of the P7 porousparticles. This composition was foamed (aerated) and the resultingfoamed aqueous composition was coated onto a surface of the poroussubstrate described above with a coating knife with a 1.52 mm (0.060inch) gap as described in Comparative Example 2. The dry foamedcomposition of the foamed, opacifying element contained 11.91 weight %of the P7 porous particles, 0.0989 weight % of carbon black, and 0.165g/m² of carbon black on a dry weight basis. This inventive foamed,opacifying element exhibited an LBV of 6.2 that increased the opacifyingability of the thinner dry opacifying layer weight of 167 g/m² comparedto the previous Invention Examples, and the luminous reflectance valuewas 43.

INVENTION EXAMPLE 7

A foamable aqueous composition was prepared according to the presentinvention with 881 grams of EAGLEBAN® FRC-0307 Drapery Compound, 114.1grams of a 49.25 weight % aqueous dispersion of the P7 porous particles,and 4.91 grams of a 51.1 weight % dispersion of the P4 porous particles.This composition was foamed (aerated) and the resulting foamed aqueouscomposition was coated onto a surface of the porous substrate describedabove with a coating knife with a 1.52 mm (0.060 inch) gap as describedin Comparative Example 2. The dry foamed composition (dry opacifyinglayer) in the foamed, opacifying element contained 10.81 weight % of theP7 and the P4 porous particles, 0.0859 weight % of carbon black, 0.0231weight % of yellow tinting colorant Y2, and 0.161 g/m² of carbon blackon a dry weight basis. This inventive foamed, opacifying elementexhibited a very high LBV of 6.7 and increased opacifying ability of thedry opacifying layer weight of 188 g/m² similarly to Invention Example6. The luminous reflectance value measured for this inventive foamed,opacifying element was 44 and the measured b* value of 0.46 reflects thepresence of the yellow tinting colorant.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

1. A method for providing a foamed, opacifying element, the methodcomprising: providing a foamable aqueous composition that has at least35% solids and up to and including 70% solids, and comprises: (a) atleast 0.05 weight % and up to and including 15 weight % of porousparticles, each porous particle comprising a continuous polymeric phaseand a first set of discrete pores dispersed within the continuouspolymeric phase, the porous particles having a mode particle size of atleast 2 μm and up to and including 50 μm and a porosity of at least 20volume % and up to and including 70 volume %, and the continuouspolymeric phase having a glass transition temperature greater than 80°C. and comprising a polymer having a viscosity of at least 80centipoises and up to and including 500 centipoises at a shear rate of100 sec⁻¹ in ethyl acetate at a concentration of 20 weight % at 25° C.;(b) at least 20 weight % of a binder material; (c) at least 0.0001weight % of one or more additives comprising a surfactant; (d) water;(e) at least 0.001 weight % of an opacifying colorant different from allof the one or more (c) additives, which opacifying colorant absorbselectromagnetic radiation of all wavelengths of from 350 nm and up toand including 800 nm, all amounts based on the total weight of thefoamable aqueous composition; aerating the foamable aqueous compositionto provide a foamed aqueous composition having a foam density of atleast 0.1 g/cm³ and up to and including 0.5 g/cm³; disposing the foamedaqueous composition onto a surface of at least one supporting side of aporous substrate; drying and at least partially curing, simultaneouslyor in any order, the foamed aqueous composition to provide a dry foamedcomposition; and densifying the dry foamed composition to provide a dryopacifying layer of a foamed, opacifying element.
 2. The method of claim1, further comprising: after densifying the dry foamed composition,further curing the dry opacifying layer.
 3. The method of claim 1,comprising: aerating the foamable aqueous composition by introducing airor an inert gas into the foamable aqueous composition in a controlledmanner.
 4. The method of claim 1, further comprising: cooling thefoamable aqueous composition below ambient temperature during aerating.5. The method of claim 1, comprising: disposing the foamed aqueouscomposition onto the surface using a coating process.
 6. The method ofclaim 1, comprising: densifying the dry foamed composition by acompression calendaring operation, pressing operation, or embossingoperation, or a combination thereof.
 7. The method of claim 1,comprising: aerating the foamable aqueous composition to provide thefoamed aqueous composition having a foam density of at least 0.15 g/cm³and up to and including 0.4 g/cm³.
 8. The method of claim 1, wherein thecontinuous polymeric phase of the porous particles comprises at least 70weight %, based on the total polymer weight in the continuous polymericphase, of one or more polymers derived from one or more of celluloseacetate, cellulose butyrate, cellulose acetate butyrate, and celluloseacetate propionate.
 9. The method of claim 1, further comprising:disposing a non-opacifying layer on the dry opacifying layer.
 10. Themethod of claim 9, wherein the foamed aqueous composition and thenon-opacifying layer are disposed on the porous substrate using a bladecoating, gap coating, slot die coating, X-slide hopper coating, or knifeon roll operation.
 11. The method of claim 1, wherein the dry opacifyinglayer is the only layer on the porous substrate, and is disposed as thefoamed aqueous composition using a blade coating, gap coating, slot diecoating, or knife on roll operation.
 12. The method of claim 1, whereinthe opacifying colorant in the foamable aqueous composition is a carbonblack that is present in an amount of at least 0.003 weight % and up toand including 0.2 weight %, based on the total weight of the foamableaqueous composition.
 13. The method of claim 1, wherein the foamableaqueous composition comprises at least 0.5 weight % and up to andincluding 10 weight % of the porous particles that have a mode particlesize of at least 3 μm and up to and including 30 μm, based on the totalweight of the foamable aqueous composition.
 14. The method of claim 1,wherein the foamable aqueous composition has at least 40% solids and upto and including 60% solids, and wherein: the continuous polymeric phasecomprises at least 70 weight % and up to and including 100 weight %,based on the total polymer weight in the continuous polymeric phase, ofone or more polymers derived from one or more of cellulose acetate,cellulose butyrate, cellulose acetate butyrate, and cellulose acetatepropionate; the porous particles are present in an amount of at least0.5 weight % and up to and including 10 weight %; the binder material ispresent in an amount of at least 30 weight % and up to and including 50weight % and has a glass transition temperature of less than 25° C.; theone or more (c) additives further comprise an optical brightener in anamount of at least 0.01 weight % and up to and including 2 weight %; andcarbon black is present as at least one opacifying colorant in an amountof at least 0.003 weight % and up to and including 0.2 weight %, allamounts being based on the total weight of the foamable aqueouscomposition.
 15. The method of claim 1, wherein the one or more (c)additives of the foamable aqueous composition further comprise anoptical brightener that is present within: the continuous polymericphase of the porous particles; a volume of the first set of discretepores; or both the volume of the first set of discrete pores and thecontinuous polymeric phase of the porous particles.
 16. The method ofclaim 1, wherein the surfactant of the one or more (c) additives in thefoamable aqueous composition is a foaming agent and the one or more (c)additives further comprise a foam stabilizing agent.
 17. The method ofclaim 1, wherein the one or more (c) additives of the foamable aqueouscomposition further comprise a tinting colorant that is present in anamount of least 0.0001 weight % and up to and including 3 weight %,based on the total weight of the foamable aqueous composition.
 18. Themethod of claim 1, wherein the one or more (c) additives of the foamableaqueous composition comprise an optical brightener in an amount of atleast 0.01 weight % and up to and including 2 weight %, based on thetotal weight of the foamable aqueous composition.
 19. The method ofclaim 1, wherein the one or more (c) additives of the foamable aqueouscomposition comprise two or more materials selected from a foamingagent, a foam stabilizing agent, a tinting colorant, an opticalbrightener, a flame retardant, an antimicrobial agent, and an inorganicfiller.
 20. The method of claim 1, wherein the one or more (c) additivesof the foamable aqueous composition comprise an antimicrobial agentcomprising silver metal, a silver-containing compound, copper metal, acopper-containing compound, or a mixture of any of these.
 21. The methodof claim 1, wherein the dry opacifying layer of the foamed, opacifyingelement has a light blocking value of at least 4 and a luminousreflectance that is greater than 40% as measured for the Y tristimulusvalue.